Let's not call Crocodile low tier. Oda has already said his biggest regret is having luffy beat a warlord (crocodile) so early in the story.
I'm sure if asked to provide a canonical justification for crocodile's performance, it would be that his spirit was crushed and he was completely off his game, physically and mentally.
Crocodile is apparently pretty notorious even among the New World, so take his showing at Marineford to be more in line with his ret-conned "real" strength.
I feel like, as far as current/former warlords go, buggy and moriah are meant to be the weakest. Not including blackbeard, weevil, or Boa, you can separate the others into two tiers:
Tier A: Mihawk, Kuma (pre-cyborg), Doffy
Tier B: Crocodile, Law, and Jinbei
And they're all strong enough to be at least leading members of a yonkou's crew.
Boa could fall in either tier
I'm sure if asked to provide a canonical justification for crocodile's performance, it would be that his spirit was crushed and he was completely off his game, physically and mentally.
Crocodile is apparently pretty notorious even among the New World, so take his showing at Marineford to be more in line with his ret-conned "real" strength.
I feel like, as far as current/former warlords go, buggy and moriah are meant to be the weakest. Not including blackbeard, weevil, or Boa, you can separate the others into two tiers:
Tier A: Mihawk, Kuma (pre-cyborg), Doffy
Tier B: Crocodile, Law, and Jinbei
And they're all strong enough to be at least leading members of a yonkou's crew.
Boa could fall in either tier