Zaran
Adventurer
Or demons, or immortals. You know, pretty much every monster that is available at epic tier (especially post-MM3, your options for new maths and new power design epic creatures are chronically limited to say the least). I wouldn't find this HALF the issue I do if I had viable epic fey, or viable epic anything except demons/undead (immortals only tangentially actually).
Also it's the whole fact that it's also a minor action by this point that is a huge problem. You can minor action use it, bunch all the enemies up and then dump a standard action astral storm on them.
I honestly think if you never saw this in play it's hard to how broken it got. Especially when you consider OTHER characters exploiting everything being bunched up to drop AoEs on them too.
While I will admit that it was a bit too powerful but they went too hard with the nerf bat beating. They can say better to nerf too much than not enough but when they hardly ever make changes to increase power this is bad change.