Victory is based on the number of healer in the alliance.

[silverlunarfox]

Frontline:

Some alliances doesn't have a single healer where some others may have 7 or 8 in it, when that's happend you'll know from the start who will win.

Either put a limit to how many can be healer in a group or try to Distribute properly the healer in both nations.

That also mean make it unable to switch job in the instance.

You can switch classes in the spawn area. This falls on the players not SE to fix. If theres more than two healers or tanks, I switch. unfortunately most are in it for levels and won't. But I have been on healer bare alliances and have still won. Just gotta run smarter.