Alright.
I have seen this debated to death over card text and cross-references to the rule book text and blah blah blah, but never any official word.
If I land a hit on you with my ion cannon and you still have 25 shield tokens guarding your precious snub fighter, are you still ionized after losing a shield token to damage, or do I have to widdle away all of your shields to ionized you?
Personally, I'm an old school X-Wing and TIE Fighter on PC type of gamer (floppy disks 4 life!), so my roots tell me you need to blow away the shields first before you can hit the hull with any sweet ion action.