I am not talking about normal warzones. But in ranked arenas, if one team have guard that they shouldnt have, considering the team composition, then its a huge deal. Even more if he puts on a tank gear. I admit, I dont play any of those classes, so I cant say for sure. But lets take guardien, when you are in soresu with vigilent talents, you still can use Plasma brand, overhead slash, you still get proc to dispatch and master strike, the only thing you lose is unremitting and some %dmg from not having shien form on. I am using skill calculator for this, and there is no mentioned you couldnt use those abilities with soresu form, but I didnt try it, so if I am wrong just say so.