Oh, no. Abyssal Drain is a massive MP drain. You'll still want to pull with Unmend/Unleash to establish hate, then use Abyssal Drain on large packs. It's basically your "I pulled the whole room, now I need to contain this mess and stay alive," button. Keep in mind, you only get the HP absorption if you Dark Arts it, which you'll want to do. I usually run ahead and Unleash packs, then once I've settled into my spot, pop a cooldown, Blood Price and Dark Arts + Abyssal Drain until low on MP.

Sole Survivor's effect triggers on mobs, not players. You want to toss it on whatever mob is closest to death to get the benefits. I use it mostly on trash pulls so I can keep spamming Dark Arts + Abyssal Drain and let the healer DPS more.