Hello i love arcanist And combination with occultist feel just right, But IT Is a way to make mend flesh more reliable? It looks to me too random for hardcore.
If you’re already familiar with the modding tools, on the top of my head you can try to turn the mend flesh skill into a skill like Blood of Dreeg but without the other buffs other than healing. Essentially turning Mend Flesh into an AoE heal that will heal everything near the bird instead of just 1 target and thus more consistent healing. Downside is its kinda op without some number adjustments and i have no idea if that heal skill slot works with this kind of abilities (might have to modify the pet and add it as specialattack or smth maybe, if it even works. Never tried it myself).
put him on defense is the best way as far as I know. or as said mod him.