I played foh and bosses were a little tough. I'd go grief hoz on switch

20 foh bolt fana hs 1 into smite

1 into smite and fanta should be fine if you have a good smite setup on switch. The smite is just to deal with bosses and the pesky immunes that wont break from foh

Then your a5 merc should take care of mobs of beasts that wont die from holy bolt splash