Can confirm, which others have done also, Horns of War is easily soloable by BST with Gerard. Can usually get through with only 1-2 rewards and have never used mulsums. Nothing spectacular about my gear either -- 2x astolfo axes and salade with -10% pet damage taken is all I'm using. Got a few screenshots of Meteor doing less than 100 to Gerard. 0/3 on tongue so far but shanks selling pretty quickly at 900k-1m each.
edit -- tongue 1/4!