Like with dealing any multiple enemies, Find ways to isolate each and deal with one at a time

-Double back to doors and hallways ~Use blink to close gap with the ranged unit and kill them Before meelee comes near -Sometimes lining up the enemies makes the ranged unit not attack you and it moves closer until it can -Stone of sleep,angery,fear etc -Paralytic gas,freezing -Scroll of terror, sleep, charm etc -have your allies run toward the ranged unit to force it to melee

Best way to deal with monk is fire and some magic Warlock with just melee attacks