How could you do this to AST?

[Karshan]

And they may change that now so they don't hurt Sage and Scholar being able to work together.

They won't though, due to the very way some effects are coded in this game ("if dmg <> 0 then debuff" wouldn't even surprise me lol). This would allow a lot more cheeses on strats.
See E10S tourniquet shield cheese and imagine that on a lot more mechanics. Or how some tanks can cheese with invuln due to taking 0 damage (PLD, GNB) and others can't because they take damage so the debuff anyway. And imagine that stacking shields could sometimes work as those invuln with sufficient mitigation (reprisal, addle etc...)