Tracer can recall to high ground. Bastion and Solider can rocket jump. For Cass to be viable, he needs some kind of vertical movement. At least Torb can throw his turret vertically. I would give Cass a rope lasso that let’s him pull himself slowly up to high ground.
Recalling to highground doesn’t count, and Soldier runs to highground 90% of the time not rocketjump. This is not a big deal at all.