The 4 piece DPS set bonus has undergone a few major changes. Changing it from buffing Army of the Dead was a pretty solid move. Army of the Dead would probably need some pretty massive changes (or at least non-taunting made baseline) to be worth using even with the original duration bonus. That said, parses on this Soul Reaper change suggest it's a little underwhelming in total damage done. In theory, I think the mechanics aren't completely out of line. 2H frost is probably where this bonus gets a little bogged down. Because using that single rune messes up 2H frost's rotation a bit (which is almost exclusively based on using Obliterate, which costs 2 runes), it could lead to some confusion. There's also the issue of lining up a 6 second cool down with a Killing Machine proc. In many cases, it would lead to a DPS loss to "wait it out" for that line up. Still, this could probably end up a decent bonus. Parses just suggest it needs a little bit of a boost to make it more desirable. Perhaps providing some extra guaranteed damage boost might work.
Tier 15 death knight tank bonuses
The 2 piece tank bonus is very, very basic. You can use Rune Tap a little more often. Hey, that's free healing, right? Alas, 10% Free healing is still pretty low on the totem pole, so that makes it a little less desirable. The problems, though, really become evident when you compare it to the other tank classes. Warriors, Paladins, Druids, and Monks all get dynamic bonuses that allow some powerful interplay between multiple abilities. It really feels like this bonus needs a revamp to either make Rune Tap a bit more powerful, or to offer a more dynamic play style change like the other tank 2 piece bonuses.
The tank 4 piece bonus comes out to 90 runic power per bone shield, which, depending on avoidance, can come very slowly. A few extra Rune Strikes isn't really a hugely exciting prospect. It's possible you could see this is an opportunity to use Conversion, but Conversion still specifically blocks extra runic power generation from Scent of Blood, so it's not clear that would actually be desirable. You could also possibly consider it extra healing if you give up Purgatory for Lichborne, but that's not a given for every death knight. In short, this set bonus really underwhelms at the moment, especially since it would require picking specific talents to get the theoretical most out of it.
Other new patch notes
Death Siphon now heals for 150% of the damage dealt (was 100%).
Conversion now costs 5 Runic Power plus 5 per second thereafter (was 10 Runic Power plus 10 per second).
The Bloodworms summoned by Blood Parasite now have 200% more health and heals for triple the amount.
Strangulate's cool down has been reduced to 60 seconds, up from 120.
The changes to the healing talent tier are probably much needed. Death Pact
has been the overwhelming favorite so far for most death knights, due to the amount and versatility of the heal, and the fact that it has a much less immediate effect on a death knight's available resources than the other two. Sparing a Raise Dead
cool down, while it could reduce DPS a bit for frost and blood if you don't summon it with your buffs
up, is much less problematic than giving up a death rune or essentially suspending the traditional rune regeneration mechanics and extra DPS provided by your runic power dumps. Death Siphon becomes a much more tempting choice now, especially for unholy, which can spare the death rune easily and may prefer keeping their ghoul out of the red zone, health wise. Conversion, I think, still blocks out a lot of DPS and threat (and, in the case of Scent of Blood, survivability), and probably won't budge much, I fear.
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