Another way to do it, it’s others using stuff like cb/static field plus survivability and the one with highest mf could invest also in damage. That way the others would make party members impact on overall damage while the killer would have the highest damage output and mf effectively killing everything.
paladins and barbarians can do that job really well with cb and sorc with static field. Other classes can do fine also, the most important stuff often would be:
cb, static field, open wounds and maybe some curse wand or necro to improve the damage of the damage dealer.
If you’re killing bosses, merc would be really bad, while if you’re focusing on named monsters(non-bosses) mercs could be useful if you stack enough damage and mf on it.