If you can't do Ultimates, you're not going to LMB anything. So grab whatever you can that will make you stronger.Medusa Rag is ridiculously strong.
As said by others, a friend with Behemoth will get you one turn. But you'll still take damage from AoE. Ultimately, it's a DPS check - can you get to Full Burst while still alive (and not stoned) or not?
Rahab is very much the same, but not as bad. Those without Sol/Pumpkin Artemis are pretty much boned since she just goes apeshit on your ass in just a few turns. It's still possible to beat even without them, but you're just going to need be very strong.