YESSSSSS!

30 Res is respectable but not enough to consistently ploy with, it's kind of right on the fringe. Even so this is still a solid Ishtar you have and definitely worth building.

Congrats, just give her fury to increse the Res stat if you want to use ploys

Nope. Only 36 or higher can consistently ploy.

ABSOLUTELY NOT!!!!!
Even with fury boosting it up to 33, it just isn’t high enough to respectably ploy, ploys would need units with at least 36-40 res range or higher to reliably ploy

30 res is enough if you're trying to ploy melee units other than dragons, which means res ploy probably doesn't make sense with that much. If you switch to fury, you're up to 33 so the mid-to low-res mages will get hit except when you're up against inflated PvE stats (but I don't recommend ploys in PvE anyways. Just too many enemy units and it's hard to cover enough squares.)