Sorry, unclear question.

What I meant was: "Why does DRK need to be MT in order to deal max damage", exactly? Because TBN can be used on anyone, if it needs to be used at all - you can just not use it if you feel it's hindering your DPS (which it shouldn't, if used in its intended use: burst damage, not sustained damage). There are no other skills working on damage received that concern even remotely DPS on DRK.