To me the highest priority issues that need to be addressed as soon as possible are:
- Living Dead, it's just not on par with other tank invulnerable abilities and needs to be reworked to make it less convoluted and to not have unnecessary penalties.
- The Blackest Night needs it's duration increased slightly to compensate for the increased shield strength so that it doesn't become too difficult to break, especially when we start out-gearing content. Just going from 7s to 8-9s should hopefully be enough.
- Something needs to be done about DRK's burst self-heal in single-target situations. Abyssal Drain is great for packs of enemies but it's heal is ineffectual in boss fights.

There are other things that I am uncertain about but I would have to see DRK in actual play after release to form a proper opinion.