As a light tweak, what if they just reduce the Soaring effect on healers? What I see so far is you'll get healers that follow a small team keeping them alive to build up to 10S, then they can pretty much juggernaut their way around. If attacked, the other healer and their DPS can stop the attacker. Mechs won't last long against them either. And if there's multiple healers within that group, that negates nearly any counteroffensive momentum.

Looking back to Frontlines for a moment, healer stacking was still an issue, but you didn't have healers with 20% decreased damage taken, increased damage dealt and increased healing. So maybe that's one good place to start?