I think the setup you have for the mobs, where they only take the one flinch, is much better and more of a challenge without a doubt.
i play Tao mostly on the server, so i cant say to much about T-storm for wizzies on here.
But i do know, if i was playing wizzy and there was no flinch, i just wouldn't bother even learning t-storm. Honestly i'd say wizzies would just get battered.
On euro, T-storm was my goto grinding spell, You'd always have your wizzy buddy you would go t-storming with and the lazy assed warrior buddy looking to be leveled by luring for ya.
Only thing i can think of to counteract it without touching flinch is add like a 1sec para or 0.5 sec para to the skill, dosent hit too many mobs so dont think that would break it.
But all in all, i dont care im a tao.. wizzies have it too easy as it is, can just run round with firewall and lightning and many other options.. so F**K them
