Advance warning: I'm verbose. The bullet list in the middle should work as a passable tl;dr, though.
I've been playing with the new Disruption Shield for a while now, and although I still haven't beaten the game (got careless while doing a vault in the prides), I do feel like I've got a pretty good idea of how the game plays for an archmage that relies on Disruption Shield as its main defense. And I gotta say, it's actually a pretty cool playstyle. It's got good durability, although you wind up relying a lot on active (and reactive) defenses, and it also lets you use all those expensive spells the archmage has. Indeed, it practically requires semi-regular usage of a spell like Inferno or Time Prison, especially if you wind up being aggressive rather than hiding and sniping.
Basically, the way I ended up playing was running around with Disruption Shield up at all times, and my mana fairly low (I generally aimed for 50 to 150 mana, depending on the situation). That way, when combat started, I could absorb a few hits without suffering life damage or seeing my Disruption Shield fail (it's very, VERY important that it doesn't). Then, once I do see an enemy, I'd generally end up basing my choice of spell on my current mana reserves - and on how deadly I perceive the thing to be. Corrupter? Inferno, Arcane Vortex, etc., to eat through the bone shields and burn off some mana. Maybe a Displacement Shield to burn mana while simultaneously protecting myself from damage. On the other hand, if I'm just facing a critter, I'd generally just use basic attack spells, unless my mana was running too high.
I also ended up loading on everything I could that would boost my spellpower and maximum mana, even to the detriment of immunities and HP. By the end (level 42), I was running around with nearly 700 mana, and my spellpower and Spell/Arcane mastery were high enough that I was regenerating only 0.16 or 0.17 mana per point of HP damage. That wound up being pretty durable, and although I did have a few close calls, the skeleton I was running had enough life that I was never worried about having too little HP. I really should've had some more stun and confusion immunity, though - THOSE were big problems.
Talent selection is fairly flexible, although there are some that I think are particularly useful:
- Displacement Shield and the Shielding talent from the Aegis tree are a MUST. Get these and max them ASAP, then make sure they're always active. My whole playstyle was built around these two talents, and I didn't really find it viable to use Disruption Shield as my primary defense until these were both nearly maxed. You might even consider spending some category points on Spell/Arcane to boost Disruption Shield even further, if you can afford it.
- You need back-up shields, because sometimes you'll need to spend a few turns just burning off mana. Secondary shields will often buy you enough of a respite to do so. Shielding runes, Displacement Shield, Time Shield, and the like are all quite useful. Aegis is also a great investment. I found myself using two good Shielding runes as my first backup, with Aegis when I needed to reinforce them (especially since it's got a high mana cost and is instant cast). Displacement Shield was also quite useful, since it's nice and beefy, lasts a long time, and is moderately expensive in terms of mana. Lastly, Time Shield is another instant cast spell with a high mana cost, that'll let you delay damage a few turns (Shielding rune + Time Shield + Aegis is a nice way to burn some mana and throw up shields, without spending a turn).
- You'll also want some spells with high mana costs, because in a hectic battle, you'll want to be burning as much mana as you can. I was quite fond of Inferno, Time Prison, and some of the aforementioned shields for this.
- Metaflow is an amazing panic button, especially if you put at least 4 points into it. At that point, you can use it to take expensive spells off cooldown (while spending a hefty chunk of mana in the process, too!); take emergency spells (Phase Door, Teleport, shields) off cooldown; or drop Disruption shield, and then have it available again the very next turn.
- Spells with moderate mana costs and moderate cooldowns are also quite useful. Arcane Vortex, Flameshock, Fireflash, Mudslide and Chain Lightning were all quite nice.
- I'm pretty sure that Quicken Spells and other cooldown reducers will be handy, as well, though I haven't actually invested heavily enough to notice, yet.
Durability was, overall, really high. Generally, if you can last long enough for Inferno or Time Prison to come off cooldown naturally, you'll be able to last through the fight. Eternal bone giants are annoying, more than a threat. However, there were some things that were pretty harmful - namely, anything that turns off Disruption Shield, or prevents you from freely using spells. Stun was pretty nasty, as was confusion. Ditto with silence. And Mana Clash has the potential to be particularly scary - you're risking loss of all sustains (including Disruption Shield) if your mana is too low, and you're risking a massive mana storm if your mana is too high.
Speaking of mana storms... they can be pretty scary. I ended up killing one of the backup guardians (as I was dying) with a mana storm doing 1222 damage per turn. If something like that hits, you'll want to throw up all the shields you can, and pray that nothing kills you before you can get Disruption Shield back up. Also, if you die when one of those is raging, it'll still be there when you come back - and you won't have your arcane resist any more (not sure if that's intended behavior). If you were sent to the eidolon plane, you might be able to survive, with use of heavy shielding. Might still lose a second life, though. But, the Blood of Life is essentially useless against really powerful mana storms. So, try and reset Disruption Shield every so often, if possible.
In terms of race, I ended up playing a skeleton, but I think there are probably better choices. Bone Armour and Reassemble were handy, but I didn't end up using them too much, and Resilient Bones is a nice way to lower harmful durations (including mana storms!), but I was also hurt by being unable to use Wild infusions to end statuses. Next time around, I'll probably go Cornac (for the category point - strong Disruption Shields), Yeek (confusion resist and global speed boost), Dwarf (save bonuses), or Shaloren (Timeless, for stun duration reduction and for boosting Shielding runes).
The one thing that I'm not quite happy with is that my build ended up being pretty close to a classic fire mage nuker. I don't think Disruption Shield builds are necessarily more unbalanced than the typical archmage, especially given that I found it easy to make a single slip that ended with me dying, but I do think it would be better if it weren't possible to use close to the same build for both a defensive Disruption Shield mage, and for an offensive fire mage. I think the big issue is that Inferno is so massively expensive mana-wise, and has such a big AoE, that I end up going heavy in the Fire tree and maxing Spellcraft, just so I can burn mana in any room. And at that point, going fire-heavy is too tempting. Plus, the previous talents in that tree are also pretty good at using up mana. I think reducing Inferno's mana cost (and maybe increasing the cooldown) would help a lot with that. The Air tree could also use some tweaks, IMO - Thunderstorm is promising, and I did try it briefly, but quickly decided it wasn't worth it. Not that strong, really expensive sustain cost, and the mana drain wasn't that great. Plus, Feather Wind isn't all that great. Cutting the sustain cost on Thunderstorm to 70 mana and doubling the per-turn mana drain would help encourage people to take that over fire spells, I think. 12 mana/turn drain is worth it at a cost of a 70 mana sustain, IMO; I didn't think 6 mana/turn was really worth reducing my capacity by 170, though.
. Then again, I had optimized myself a fair bit for high mana, high spellpower, and high mastery in the Spell/Arcane tree.