You could also use the Martyr Wraps. Binlor, too, although piety gain for him is difficult without using glyphs (but the same can be said for JJ). Maybe also Whurgarbl, if you're able to tank well enough.
Martyr wraps and whurrgarbl won't cut it on harder difficulty levels, at least not without some physical resistance. Binlor would be an incredible challenge to get piety with, and even then stone heart requires an exorbitant wall consumption. Since you won't be grabbing boost mana as a warmonger, JJ's piety gain shouldn't be a big issue.
For the record, the exact PQI scenario I had was warmonger gnome berserker on Ick Swamp. I prepped trisword to basically turn him into an orc variant and chugged my mana potions as soon as I created them. I found the goo boss twice in a row (late in exploration the second time around) and had no real way to approach him.