Now that I can finally log in and post again, I'll offer some thoughts I jotted down a couple weeks ago.
Core Abilities: Really disappointed that the form toggles are down here, forcing AP to be spent on lousy forms that I never intend to use. If either the AP cost on everything but the capstone was removed, or the chain dependencies between them were severed, this would cease to be an issue. Core Abilities (in all trees) either need to be universally viable, free, or de-chained.
Necrotic Touch/Bolt/Blast: Why were the cooldowns on these doubled? They were weak enough to begin with. I really wish something had been done to make these worthwhile in epics, such as the ability to invest 2/3/4 points in them to unlock Heighten/Empower/Maximize toggles to affect them. As it stands, these are not worth 6 AP. More options to build towards DPS rather than DC should exist: build options are good.
Cloak of Night: This is not worth any AP. Reducing the DPS I take from a few sources of damage, while simultaneously reducing the HPS I receive by the same amount against all sources of damage, is at best a wash and in most practical situations will only hurt my survivability.
Spell Critical: Negative Energy: This needlessly uses up a lot of real estate. Just make this a single 4/4 enhancement to save space.
Skeletal Knight: Can't test right now as this crashes the game, but 15 AP total investment for something that is almost certain to be garbage in epics (this game has always been quite anti-summons) looks like a waste of so much tree real estate.
Master of Death: this is a fairly lame capstone. Undead healing augmentation is not really needed, as PMs are already very survivable and 5% bonus here is hardly noticeable (and considering the Tier 1 Negative Energy Conduit gives 10%, this seems even weaker in comparison). The old capstone (AM capstone now) was far more useful than this. An example of something capstone-worthy would be the ability to convert negative levels, instant death attempts, and negative energy damage into evil damage against things that are death warded. For instance, each negative level that death ward blocks could be converted into 100 evil damage. Each failed save vs instant death that is blocked by death ward could be converted into 1000 evil damage. Negative energy damage that is blocked by death ward could be converted into evil damage at a 1:1 ratio.
One thing I had hoped to see: An ability to repair stat damage while in undead form. A remedy for this is long overdue.
Overall, this tree delivers what is required from it, but lacks any new wow/fun factor. Raise Ally is a fun idea, but I don't foresee actually using it.
SLA's (Core Abilities): An inability to take SLA's from your secondary school, or from tertiary schools, will I think effectively kill Archmage as a primary PrE -- I see no compelling reason to play anything other than a primary PM with a dabble in AM for 1 school's SLA's, crit chance and metamagics. On live, an AM can take not only SLAs from his secondary school, but also the level 1 SLA's from any tertiary school he wants (as these require nothing other than the appropriate spell focus feat for that school). For instance, a primary evoker can take the web SLA if his secondary school is conjuration, and also pick up Hypnotism and Necrotic Touch SLAs by taking the enchantment and necromancy spell focus feats. This is a huge loss for Archmage. I don't think this issue can be repaired for as long as these SLAs remain Core Abilities, thus they must be moved elsewhere.
Efficient Metamagics: Break the chain dependencies on these. As it stands, reaching Efficient Heighten would require taking 3 other metamagic feats, and then further spending AP to reduce their cost. I should not have to take the Enlarge or Quicken feats on top of Maximize and Empower, and then cheapen them all, just to take Efficient Heighten. Furthermore, there is no such dependency between metamagic cheapeners on live.
Arcane Bolt/Blast: I really wish something had been done to make these worthwhile in epics, such as the ability to invest 2/3/4 points in them to unlock Heighten/Empower/Maximize toggles to affect them.
Spell Penetration: Condense these into a single enhancement so they don't take up so much space.
Primary School Focus (first rank): This comes pretty late in the tree (leveling concern). If Spell Penetration is condensed into the first tier, this could be moved down a tier, or maybe 2.
Spell Critical Chance: While I appreciate this being more freeing than the corollaries in the Savant Trees, I would appreciate it even more if these could offer a 4/4 investment per enhancement; thus, you could, at your discretion, choose to take +8% crit chance in 4 different lines simultaneously for 32 AP. We need more choices not less.