Well First off, they have to hit us...so as long as you stay out of their range, you will be able to cast. (So basically other mages and bards are your issue).

Secondly, we mages have, binding spells/knockback spells/sleep spells and gravity spells that make it easier for us to keep our distance from foes.

We also have Swiftcast/Surecast abilities and instant spells

WHM's have Benediction
SCH's/SMN's have pets that do their own thing and will need to be dealt with by the opposing party

WE have Shield-skills that protect us from damage Manawall/Ward/Stoneskin etc (Not sure If SS will keep our spells from getting interrupted but if it does )

Lastly, this isn't a 1:1 thing. There are 3 other people in your party they need to deal with...and nothing was said about Raise not working in PvP battle.

I see this as a 'bring it on' thing...not a 'oh we're screwed' thing.