Personal opinion here, but I think Cataphract is always meant to function as a secondary healer with the benefit of giving themselves stacking prot, or a backline damage dealer. But never as a solo healer.

They're a she, by the way.

thought they were a girl

Maybe it's because the mods I use but I found him very appealing with his wee AoE heal. To me he is a punchbag that helps me sustain through long runs helping my main healer to focus on the more damaged character. Since he does AoE heals, even an increase of a single extra point of HP healed through each upgrade of the skill is massive since it hits all 4 team members, specially with a relic that increases healing effectiveness. I've reached at point where he was healing 48 hp across the board in a single turn, and I think the only way to balance bigger AoE healings is to add a cool down to the skill of at least a turn or maybe two.