Summary:
Fantastic THF damage
Decent self-healing melee
Superb damage avoidance
Good damage mitigation

There are two variations of this build, based on the past life you prefer. The efficacy of the build does not change with your choice:

Fighter past life: 9 Fighter/9 Monk/2 Druid
Monk past life: 10 Monk/8 Fighter/2 Druid

Here's the benefit breakdown:
Fighter 8: Kensei increased crit range, any melee weapon as a ki weapon
Monk 9: 15% movement speed, Improved Evasion, access to Ninja Spy and Shintao enhancements
Druid 2: 5-min Ram's Might, Magical Training feat, access to Empower Healing Spell feat, access to Nature's Warrior enhancements

I personally want a monk past life, so here's the breakdown for that version:

Human 10 Monk/8 Fighter/2 Druid:
1 Monk 1 (Human: Dodge, Monk: Power Attack, Level: Cleave)
Skills: Balance 4, Concentration 2, Swim 1, Tumble 1, Spot 1, Move Silently 1, Heal 2, UMD 1
2 Monk 2 (Monk: THF)
Skills: Balance 1, UMD 1.5
3 Druid 1 (Level: Mobility)
Skills: Heal 4
4 Monk 3
Skills: Balance 2, UMD 0.5, Heal 0.5
5 Monk 4
Skills: Balance 1, Concentration 1, UMD 0.5, Heal 0.5
6 Monk 5 (Level: Weapon Focus)
Skills: Balance 1, Concentration 1, UMD 0.5, Heal 0.5
7 Monk 6 (Monk: Deflect Arrows)
Skills: Balance 1, Concentration 1, UMD 0.5, Heal 1
8 Monk 7
Skills: Balance 1, Concentration 1, UMD 0.5, Heal 1
9 Monk 8 (Level: Great Cleave)
Skills: Balance 1, Concentration 1, UMD 0.5, Heal 1
10 Fighter 1 (Fighter: ITHF)
Skills: Jump 1, UMD 0.5, Heal 0.5
11 Fighter 2 (Fighter: Improved Critical: Slashing)
Skills: Balance 0.5, UMD 0.5, Heal 0.5
12 Fighter 3 (Level: Master of Forms)
Skills: UMD 0.5, Heal 1
13 Fighter 4 (Fighter: Weapon Specialization)
Skills: UMD 0.5, Heal 1
14 Fighter 5
Skills: UMD 0.5, Heal 1
15 Fighter 6 (Fighter: GTHF, Level: Empower Healing Spell)
Skills: Balance 1, UMD 0.5, Heal 0.5
16 Fighter 7
Skills: Balance 0.5, UMD 1, Heal 0.5
17 Fighter 8 (Fighter: Greater Weapon Focus)
Skills: Balance 1, UMD 0.5, Heal 0.5
18 Monk 9 (Level: Grandmaster of Forms)
Skills: Balance 5, UMD 0.5
19 Druid 2
Skills: Heal 6
20 Monk 10 <-- Swap for Fighter if you want a Fighter past life
Skills: Heal 1, Balance 3, UMD 0.5
21 Overwhelming Critical
24 Toughness
26 ED: Perfect THF
27 Epic Damage Reduction
28 ED: Toughness

Kensei (33)
1 Kensei Focus
6 Extra Action Boost III
2 Kensei Weapon Specialization I
1 Spiritual Bond
1 Strike With No Thought
3 Haste Boost III
2 Kensei Weapon Specialization II
6 Improved Dodge III
2 Weapon Meditation I
1 Shattering Strike I
2 Kensei Weapon Specialization III
2 Kensei Weapon Specialization IV
1 Reed in the Wind (filler)
1 Keen Edge
1 Deadly Strike
1 One with The Blade

Ninja Spy (11)
1 Ninja Training I
3 Acrobatic III
2 Sneak Attack Training I
1 Ninja Training II
2 Fists of Iron
1 Agility I
1 Shadow Veil

Shintao (11)
1 Bastion of Purity
2 Ki Shout (filler)
2 Exemplar II (filler)
1 Protection from Tainted Creatures
4 Iron Skin II
1 Iron Hand

Human (17)
1 Damage Boost
2 Constitution
2 Improved Recovery I
1 Dont Count Me Out I
4 Action Surge: Constitution II
2 Improved Recovery II
1 Defense Boost
2 Strength
2 Improved Recovery III

Nature's Warrior (8)
1 Nature's Warrior
3 Athletic III (filler)
1 Shifting Rake I (filler)
3 Action Boost: Double Strike

Legendary Dreadnought
1: Strength (2), Extra Action Boost II (2)
2: Strength (2), Improved Power Attack (2), Momentum Swing (3)
3: Haste Boost III (3), Lay Waste (2)
4: None
5: Advancing Blows (2), Devastating Critical (2)
6: Master's Blitz (2), Headman's Chop (2)

Twists:
Standing with Stone
A Dance with Flowers
Rejuvenation Cocoon

PRR:
10 Epic Damage Reduction feat
15 Artifact (Planar Prowess)
16 Enhancement (augment)
15 Grandmaster Earth stance
15 Standing in Stone
10 Iron Skin
-----
81 PRR = 36.2% damage reduction
10 Human: Defense Boost
03 Don't Count Me Out I (below 50% HP)
-----
94 PRR = 39.7% damage reduction (situational)

Dodge:
08 item
06 Monk
03 Dodge feat
02 Mobility feat
03 Acrobatic (Ninja Spy)
03 Improved Dodge (Kensei)
----
25% Dodge

Healing Amp:
30% Human
05% Paladin past life
15% Shintao
30% Gear
10% Ship
----
= 224% Healing Amp

Positive Spell Power:
114 Ruby of Devotion augment
075 Empower Heal Spell
046 Heal skill
024 Implement bonus
030 Shintao
------
289
024 (Delta for new ML28 138 Ruby of Devotion augment)
015 Heal skill augment
-----
328 Positive Spell Power for Rejuv Cocoon with U19 augments

Doublestrike:
03 Artifact (Flawless Black Dragon set)
06 Item (Clever)
01 Strike with No Thought (Kensei)
---
10% Doublestrike (passive)

This build has 10 uses of LD 30% Haste Boost, Kensei 30% Haste Boost and Nature's Warrior 30% Double Strike. That's 10 continuous minutes of +30% additional damage, which is plenty of go-go juice between shrines.

Gear:
Weapon: Clever, Hewer of Suffering (Red Augment: 114 Positive Spell Power)
Quiver: EE Quiver of Poison
Trinket: Planar Focus of Prowess of +3 STR
Belt: EE Girdle of Giants' Brawn (green: 35 HP, yellow: +2 insightful CON)
Bracer: 30% healing amp of Superior Parrying
Gloves: EE Nether Grasps
Chest: Black Dragon (blue: Good Luck)
Hat: EE Black Dragon +8 CON (green: 14 PRR, yellow: +1 exceptional all stats)
Goggles: EE Dream Visor (yellow: 20 Vitality)
Back: Adamantine Cloak of the Wolf
Feet: Kundarak Delving Boots (needed when soloing, or no FoM in a group)
Neck: EE Jorgundal's Collar (Green: <empty>, Yellow: Draconic Soul Gem)
Ring1: EE Ring of the Djinn
Ring2: Ancient Band (heavy fort, +7 resist)

The above is the pre-U19 gear list. With U19 gear that's been revealed so far, these are possible changes:

Ring2: EE Consuming Darkness (Seeker 12, Combat Mastery +5, Green Slot: Heavy Fort)
Bracer: EE Bracers of Twisting Shade (+7 resist, +5 exceptional Seeker, Blurry)
Gloves: PDK (30% healing amp, +2 Insightful CON)
Belt: Skullduggery Kit (10% Dodge permutation, Green Slot: 35 HP)
Back: EE Jeweled Cloak (Green Slot: ??, Yellow Slot: +8 STR)

Net change: +2% Dodge, +10 all elemental resists, +green slot, +6 balance, 25 spell absorb, +2 seeker, +5 Combat Mastery, -4 Insightful Saves, -Diversion, -2 Profane STR. The +2% Dodge allows swapping Mobility feat for Toughness, or reallocating Ninja Spy AP to increase Dodge cap by 2%.

Stats:
STR 18 (16 points) + 5 tome + 8 item + 3 insightful + 1 exceptional + 2 yugo + 2 ship + 6 level ups + 2 ED + 2 Ram's Might + 1 human + 2 Profane = 52
DEX 14 (6 points) + 4 tome + 1 exceptional + 2 ship - 2 stance = 19
CON 17 (13 points) + 4 tome + 8 item + 2 insightful + 1 exceptional + 4 stance + 2 ship + 2 yugo + 1 racial + 1 level up + 2 Action Surge = 44
INT 8 + 4 tome + 1 exceptional + 2 ship = 15
WIS 9 (1 points) + 4 tome + 1 exceptional + 2 ship = 16
CHA 8 + 4 tome + 1 exceptional + 2 ship = 15

Note: Stats are calculated without Rage effects. There's no room to twist Primal Scream, and potions have too short of a duration for my taste. So if you have a source of Rage from someone else in the group, consider it a bonus instead of a must have.

Weapon Profile: Cleaver, Hewer of Suffering
045 3.0[2d8] base + 1.5 A Dance with Flowers + 0.5 Improved Power Attack
031 STR bonus
010 Power Attack
005 Visor
004 Conflux
006 Kensei
008 Enchantment
002 Ram's Might
002 Weapon Specialization
----
113 Average base damage
005 Advancing Blows
003 Battle Meditation (3 Kensei Core Abilities)
-----
121 average base damage (situational)
Crit Profile: 17-18/x3, 19-20/x7

HP:
025 Heroic Durability
015 Improved Heroic Durability
010 Draconic Vitality
080 Monk 10
080 Fighter 8
016 Druid 2
080 Epic
020 Vitality item
035 False Life item
060 Toughness feat x2
050 Legendary Dreadnaught
020 Yugoloth HP portion
476 +17 CON bonus
008 Nature's Warrior
----
975
020 Barbarian Past Life x2 (optional)
----
995

F/R/W Saves:
03/00/03 Druid 2
07/07/07 Monk 10
06/02/02 Fighter 8
04/04/04 Epic 8
17/04/03 CON/DEX/WIS bonus
01/01/01 Competence (Eldritch Ritual)
04/04/04 Morale (Greater Heroism)
02/02/02 Luck (Augment)
04/04/04 Insightful (Superior Parrying)
07/07/07 Resistance (augment)
01/01/01 Sacred (Blessing of the Three Dragons)
00/01/00 Agility (Ninja Spy)
00/00/-4 Yugoloth STR drawback
-----------
54/37/34
00/00/02 Monk Still Mind (vs. enchantments)
-----------
54/37/36 (circumstantial)

With Improved Evasion, just accept that you're going to always take half-damage from spell damage.

Kundarak Delving Boots address the biggest pitfall against casters: Hold Person. You're still susceptible to Command, but there's not alot of that in Shadowfell content.

Skills:
45 Balance = 23 ranks + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 4 DEX bonus + 3 Acrobatic + 3 Athletic

40 Concentration = 7 Ranks + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 17 CON bonus + 1 Agility

46 Heal = 23 ranks + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 3 WIS bonus + 3 tome + 2 Exemplar

43 Jump = 1 rank + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 21 STR bonus + 3 Acrobatic + 3 Athletic

30 Move Silently = 1 ranks + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 4 DEX bonus + 5 Competence (boots) + 5 Enhancement (Pass Without Trace)

51 Swim = 1 rank + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 21 STR bonus + 3 Athletic + 11 Enhancement (Merfolk's Blessing)

39 Spot = 1 rank + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 3 WIS bonus + 20 item

23 Tumble = 1 rank + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 4 DEX bonus + 3 Acrobatic

28 UMD = 11 ranks + 8 epic + 4 Morale (Greater Heroism) + 2 Luck (Augment) + 1 Profane (Elite Spider Cult Mask) + 2 CHA bonus

Feedback welcome.