Ok so I guess this could be considered common sense or the game working exactly as intended, but it just dawned on me last night as i was farming for my 5th or 6th hour yesterday.
For all mobs about 4500hp and under you can kill in less than about 1-2 seconds by applying a high % to proc poison (i use wound) then shiv followed by mutilate(as mutilate does a LOT more dmg when a psn is on the target) this almost always kills the target and if it doesn't it only needs like 1 or 2 more white hits.
Another bright side to this is you can move straight on to the next target and not have to worry about "Not enough Energy"
Anyways hope its helpful to some.