From a gameplay standpoint, Soraka's old Starcall was a GREAT Tank skill
Tanks want to generate threat. The longer you leave them alone, the more unpleasant they make life for you.
What better way to generate threat than with a spammy AoE MR shred attack?
I have to wonder if a similar skill will ever make it back into the game on an actual Tank. I would imagine they could make for a nice Jungler depending on what other toys they get in their kit.