This ultimate (for example) cost 225 ultimate points which in pvp is a lot for waht it does, people are using mostly in pvp skills like Soul Assault 100 points, death stroke 70 points (and this skill hits like a *** train in your face if your wearing light armor, is devastating), Dawnbreake 125 points (many magicka builds use this skill because of the stun and the aoe even if it scale with physical damage), Dragon leap 125 points and etc.
Elemental storm cost 250 ultimate points, but is a very powerfull aoe that can follow you where you move, but Negate Magick even if it very very powerfull if you catch many people inside and they dont move quick enough out, in the practice is very very avoidable.
My suggestion is to make this ultimate and maybe other ultimates too more viable in pvp, specially in BGS for example. I dont know, make a morph more cheap and nerf or change something.