It doesn't matter how powerful the healer kit is when 20+ people wail on the target. If you can save them through all of that they would be massively overpowered.

As it is, Healers are still stupidly strong in smaller skirmishes due the innate damage reduction Frontline has. It's already insanely hard to kill a competent melee Job with just few players and if they have even a single healer supporting them it become a nightmare.

Thankfully they aren't wasting resources to have separate balance for Frontlines as it is inherently impossible to make it feel good for both small and large skirmishes, the mode is broken by its very nature of being 72 player meme.