The new PvP system and Frontlines are basically incompatible. CC is fine, literally nessecary for this type of MMO but this in this match size with the limited mobility and immunities it doesn't work so well.

This is more of a Frontlines issue than the new system though. It will need some reconfiguring.

It really depended on the skill of the healer vs the ones trying to kill them.
You don't design around bad players, we have more than enough problems with what that's done to PvE in this game.