Vala turns out to be incredibly skilled with the spear and shield fighting style. She's even got attack skills that send red bolts and arcs of energy out from her spear. The legendary quality spear has a minor bleed effect on it, but against the larger groups it gives a noticeable amount of returned healing.
Misha might have felt her position was threatened, but it's not the level of healing that will replace a cleric in the group. It is enough that she can relax though. The slow damage of the demons aura effects and the few area spells the group faces is mostly covered, so she can focus on healing the Tank Trolls.
They're getting replaced frequently anyhow, as the cripple type debuff is reducing their [HP] cap every time they're hit, but Cain can't keep up with constantly replacing them without taking breaks, so they get some healing, or curse removals and switch out on small groups to keep the problem dispersed.