Never said the Oversoul doesn't come up. But if it does and you take it down, you still have 6 people instead of 5. Besides, don't you feel safer if you had 2 lives, say, for Nightfall, if someone was a Warlock in your team, you would worry less about dying but having a Titan doesn't really reassure you. But yes, it does help with Boomers, but so can shooting them and getting their agro on the balcony ledge (so they can't shoot you from that range)