Is there any cheaty way to make Mercs invulnerable?

This would be for single player. It's so annoying having them die from the stupidest stuff, I just want a companion who will stick around providing buffs, some additional damage, and a distraction.

Why Cheat Bro Play The Game As it Is. Run solo if you complain about reviving mercs

The Act 5 mercs are very durable. Give them some life leech, % damage reduction, and max res. They are quite tanky.