I'm pleased to report I didn't need to resort to tactics much and it was as I suspected, trying too much at too low a level. I came back at level 34 (I think), summoned my creature, thumped Raze, pulled the lever on the nearest chamber, whirlwind attack (dual-wielding, combined damage about 800, plus whatever multiplier I got for the attack type) at which point he tried to run away so I charged at him and he died, rather more quickly than I expected. Creature was disappoint as he didn't have time to finish urinating before it was all over.
