Healers are basically the meta for PvP right now, as doing somewhat less DPS in exchange for being virtually immortal is a bit of an unbalanced trade-off, especially when there are objectives that simply require staying alive instead of actually killing anything.

If they want PvP to ever be properly be balanced, they need to require a certain number of each role for frontlines or else people are just going to stack whatever is the most overpowered at the moment.