I don't find myself using it too much. If it included a MR debuff, I could see it being useful in the hold of roots, fear, and charm, but since it only hits DR, PR, and FR, I don't find myself pushing for it unless I am fighting a particularly high level enemy in which I am going to be laying down some heavy DPS DoTs.
It also depends on your style. If you're relying heavily on your Plague/Poison lines, then you'd probably want it more. But seeing as how when I solo, I tend to always use Fire (which has a natural negative to the target's FR check anyway), in addition to a Poison. Since the debuff doesn't do much to help the fire stick anyway, and only helps the poison, I just roll the dice and I tend to come out ahead. The mana you get set back on casting a poison and getting a resist is less than debuffing every mob you encounter.
However, that changes if you tend to fight higher level enemies, where you'll get chain resists more. I tend to aim for mobs a good bit under me that I can chain kill in massive quantities. Yet, you still have to make that spell land, so it is dicey anyway.
|