SSS has a use when you have to move away from the boss and can't hit them again within 5 seconds, it's basically free damage. However only then. TK however, has no use unless you KNOW you are going to lose stacks. (aka end of boss or before move where you're immobilized 15+ seconds). Even in dungeons against midbosses since you can just form shift and keep stacks it's never a gain to use TK. The only way I see TK being useful in it's current iteration is 700 potency. It's enough to warrant eating stacks if you need a large damage surge, but not enough to warrant buildstacks/spam it.

I kind of want to see the destruction a 4 Mnk party can use now lol.