@srrw Another, perhaps stupid, suggestion : carry pots for him, not you. I was doing p8 CS runs with my hdin (only level 89 right now) and had roughly the same problem you had. I use a Defiance merc and he’s undergeared (Duriel Shell and Steelskull). He’s only there to carry Insight, after all. I move him away and lure the enemy into my hammers when things are dicey for him (de Seis and sometimes Infector, depending on how he rolls). And I make sure to pot him when necessary. Lately, he hasn’t died a lot with this approach. The good majority of the time he survives the runs. It does make for perhaps longer runs, but when he dies, that slows thing down even more, so yeah.
In a word : babysit him. Pretty much the only thing I can do, since I don’t have all the gg gear anyway.