I have been saying stealth falls off a cliff when all toons are stealthed, everyone can be targeted.
In another thread I have stated that it needs something more going for it.
I propose mainly that stealth either gives immunity to crits, since they are harder to hit, or make the attacks undodgeable, since the enemy can't see them coming.
Both bonuses to stealth would be too much though.
Anyway, resisting TM reduction sucks offensively, but defensively yay! It's only fair.