I was bashing on this healer as a PLD, and I know my direct attacks were landing because his hp was dropping from each hit and it was showing my damage being dealt, however he was still able to cast cure II on himself. He didn't swift cast it, the spell timer bar was filling up on my screen showing he was casting it.

At first i thought it was that "Spells can't be interrupted" skill you get in pvp, but than I remembered that the cool down for it can only be, at lowest, 2 mins, and he was able to do it three times.

I even used "Spirit Within" My silencing move, and he was able to get Repose off on me with a full cast time spell. Nothing I did could stop the casting.

This has happened much more than once, and much more Frequently than the "can't be interrupted while casting" skill is allowed.