Well most skills, like in any game, are going to be sub-optimal, therefore a lot of the time making them obsolete. The only reason to have blood rain and not something better would be because you're going for a unique build, you just like it, or flavor, which is great too. Or maybe I'm missing its secret, idk :p
The discussion that makes more sense is: What are Tier 1, 2 , 3.. etc skills? Since there's technically a use for everything.
And there would be a difference in tier placement depending on if Solo or in a team. Apotheosis like the guy said could be huge in solo.
Actually, I would like to see a tier list made for the fun of it. We should make one!