DDO is ideally a multiplayer game, as indeed the pen-and-paper was better with more friends around the table. However, fortune being what it is, I gotta solo it most of the time. I'm trying to puzzle out an ideal solo build. Part of the problem, of course, is that what's ideal at the lower levels might be a handicap later - not sure, I haven't worked past about L7 yet - so it might be that "ideal" is an evolving thing that requires a heart of wood down the line to undo the thing that brought you fortune early and brings you woe later.
I'm finding for my own needs that the ideal build starts with a level of rogue - lots of skill points, lockpick and trap-disarming, good sneak and serviceable weapons and armor. A bit squishy but the sneak helps counter that if you don't mind the pace being slow and cautious. High dex offsets the armor limitation. Light punch can be offset with two weapon feat, the weapon finesse feat, and eventually the Dagger in the Back enhancement - means you don't need a lot of strength (though average strength is still recommended for carrying capacity). That means over the long term a minimum three levels of rogue. Also sets me on the road for the Thunderstone, which is also a wickedly useful way to help the Rogue survive without a fighter-wall.
The next level: cleric. I'm having a lot of good luck with at least a level of cleric to give me the ability to hunker down someplace quiet and heal up between fights. Potions are nice but expensive if you're doing mostly elite; wands are better but still not cheap if you're doing a lot of healing. You could live without the cleric level in normal mode, but normal mode is a bit - unchallenging. The shrines give me all my spell points, and there are magical items to boost those, so I end up getting a lot of mileage out of that cleric level. I'm debating additional levels - depends on whether I want those higher-level spells or want to focus on my rogue advancement.
Beyond that, I'm debating. Pulling two weapons and weapon finesse feats means either sticking to human (I actually prefer humans for the most part), throwing in a level of fighter for the accompanying feat (and the lovely range of weapons), or taking a couple of levels of ranger for the free two-weapons feat (and the lovely range of weapons). Either the fighter or the ranger option means you don't start at full capabilities, but there are long-term advantages. The ranger's conjure arrows and elemental arrows enhancements are particularly appealing, and the ranger's skill choices mean you don't tend to fall as far behind in your rogue skillset when you take that ranger level. Long-term, you eventually get some cleric spells, so maybe the cleric level can be omitted - if you don't mind struggling a bit until they show up. The fighter's added feats every couple of levels is pretty attractive as well, for alleviating the squishy with a bit of toughness and for adding a bit more combat punch. That "lovely range of weapons" bit can be pretty important when you're limited to light weapons: there seem to be a lot more magic hand-axes out there than magic sickles and kukris, and DDO's followed D&D in considering the shortsword a piercing weapon; finding a light-weapon slash combo with good magical punch for those zombies gets easier if your range of weapons is wider.
Pure rogue with a level of cleric feels like a pretty solid near-pure, keeping those important sneaking, trap-finding and lockpicking skills sharp. Cleric with a level or three of rogue is serviceable with some +# gear and magical boosts to overcome the increasingly difficult locks and traps you'll encounter, but the more rogue you add, the further behind the curve you are as a cleric. Fighter or ranger with a bit of rogue backed by cleric sounds pretty fierce - again a bit behind the pure form but a solid melee platform. There might be other options, but I know almost nothing about monks, bards, druids and suchlike, so I can't say what they might bring to the table.
Thoughts? Ideas? What path works better after the initial rogue and cleric level? Maybe ranger-rogue with a bit of cleric garnish? What problems show up at the higher levels? Back before I dropped off the face of the world for a couple of years, the level cap meant multiclassing put your top-level abilities out of reach, but the new level cap seems to encourage it, and the reincarnation bit is confusing me.