Well, I'd been missing something obvious in retrospect. I should have been going at it Karui-style - the best defence is dead enemies. DPS, DPS and more DPS. I've split the two attack skills I use over two items, each with life leech, extra melee damage and added fire damage, and switched to a heavy 2H mace that's slow (0.95 attacks per second) but does a lot of damage. It's a huge improvement in power. I take more damage if I'm hit, but I kill most mobs before they hit me and I leech loads of health. Act 1 merciless was a suicide run before, but now only the side areas are deadly. Those undead rhoas have a hell of a hard hit and they run in packs. I'm going to grind cruel docks for a few more levels and get more damage nodes.
I think I'll aim for getting a Marohi Erqi and try for a faster attacks support gem with my skills. Maybe add some dex so I can level it further.
I've still got lots of play left in this game. Superb value for money.