I have a Holosight on my GP100 .357 mag. I've destroyed two other red-dots before putting my Holosight on. It's lasted some 3000 rounds so far and is showing no sign at all of damage.
Just a couple little pointers: mount it as close to the hammer as possible. This will reduce the impact on the sight as much as possible under recoil.
BTW, the .357 mag loads I use are full house loads, old skool style. 180 gr. bullets at 1400fps. 125gr loads at 1600fps. No, this isn't a .44 mag type load, but they are stout recoil.
BTW, I use the "N-Cell" holosight. Works a charm and I like the shorter sight length.