A 24k sniper you say?
Tell him to put down the whacky baccy and step away from the high endurance mods.
A dps maxed out on high dps stat/low end modifications should barely have more than 20k in bh/camp gear.
Trust me, he's not full of high endurance stuff and he regularly does HM ops. It was a surprise for me too, but after seeing a lvl 49 sniper with 18500hp while wearing maxed primary stat stuff (and the wrong augments) I think it's not gimped at all. (edit : and btw, I now have a little more than 20k hp mostly in augmented WH with 4 secondary augmented BH pieces, Campaign will increase this at a rate of 150hp a moddable piece at least, discounting mods/enhancements only available in a certain high endurance balance - A has higher endurance than blank -, if not simply more efficient)
What is, though, is the merc's "passive heal" ability, compared to the other healers, which means we have to rely on single target cast heal (16-25% of our resource, the latter being reduced after the former has been used, but the former is on a 6s cd) alot.