Tried to solo Stone Guards in MSV-10, I couldn't kill them. The issue was not my health (I had no issue at all, the double explosion barely put me under 50% health), but the dps. When I hit berserk, I managed to survive a few seconds (9), and when I died, they were at 27% health (I had Jade, Jasper and Amethyst).
I really don't know what's the issue, because Mione killed them with a much item level than me (I'm 560) :x