Well I suppose it is a bit stronger, but not by much. Maybe its my level. I am level 20, and right now my ruin is doing 30 damage, and my drain is doing 50 damage. Except ruin has a cool down equal to its cast time. Also as far as mana goes, I honestly have had 0 issues with it. Its like I regen faster then I spend. I have 400 mana, and I almost never see it drop below full, despite frequent casting.

So aside from being able to cast drain, is there any other reason to have it on?