Cleglaw's gloves have knockback and 25% slowdown. I suppose I could try snagging a kelpie snare for my merc, though I know it's capped at 50% for bosses.
I 'm thinking that with cleglaws/kelpie snare and strafing arrows with a high cold charm would debilitate him to the point of making him a decent pincushion, like I would with my necro. I notice that with the golem/decrep and some cold casters that he's a !%***cat, even if it is a !%***cat that takes a long, long time to defeat.
I also had Guillaume's, Laying of Hands and a pair of Goblin Toes. Perhaps a bit more crushing blow would be in order, but a better bow or dropping some more of my spare points in Vitality wouldn't hurt either. I may try more out after a few days of rune/magic find runs.