Thanks for that. I'd seen the high deflection, so was looking for spells that lowered it, or kept him standing still, and that wasn't working.
My normal style is to line 'em up and keep whacking one at a time with auto-hit till they're dead - guess that won't work here.
My rogue was pretty useless anyway, and I was having some other weird problems like the Character Screen was completely garbled, so I deleted that game, and restarted with a Paladin. 10 times better, although I haven't got back to the temple yet.