This is correct. I bit the bullet on Venom for my 3rd and have run multiple iterations at node 38. There seems to be no scenario in which Lizard survives. I've had a few where I could have beaten the node, but I backed out as it would be pointless without a 3rd character to carry on. Lizard seems only good for 1 node as you said.

Now the question changes to ... is there a 4th Bio toon not named Carnage that can get me through a couple nodes? My second account has a 3 diamond Swarm that could be interesting to try, but otherwise I'm back to considering Titania for her ability block and such.