Yes, we should be tanking. Having 75 million AAV locked up in 4/5 starters means you either have young, cost controlled pitching as your 1/2 guys, or you have zero chance to be competitive. Since we dont have that cost controlled talent, we are tanking until we do.
I think it is more likely that we have 75 million locked up on the IL than 75 million on the staff performing at the 4/5 level. Corbin probably isn't a health problem, so call him a functional 5 if not in name. I think that, in Rizzo's mind, he has Corbin / Gray / Ross at least penciled in, leaving one slot for a 4/5 and another for a 6+ depth guy to fill in if Stras can't pitch and Cavalli is not ready. If I'm right, then one slot is planned for the winner of Rogers, Espino, Fedde, Voth and the other is planned for the runner up.
Personally, that looks at least one arm short, thus my wish they'd play for a Wood-level arm.