I'm actually perfectly happy with Zantetsuken as is. PvE is already so barren of interesting skills or job identity, I'm glad they went completely off the wall crazy with the PvP limit breaks. They seem to be following the Overwatch-esque design of having LBs be teamfight swinging moves, and this is exactly what it is. For a teamwipe, it also requires you to use Zantetsuken when multiple enemies have the Kuzushi debuff AND stand in a line, which is much less common than you would think. Kuzushi only lasts around 5-6 seconds in a game with 2.5~sec gcds, so imo the window for a POTG moment is actually pretty small. Any mitigation (besides guard) also nullifies it pretty hard. I'd imagine that as you climb higher into the ranks, people will also start to notice when SAMs use their Chiten, so Zantetsuken can be played around even more. I feel like as players get more experienced, Zantetsu will typically just be a "free" 1v1 kill. Personally I'm a bit more concerned with some of the tanks (see: DRK) being pretty much unkillable lol.