Haven't seen any of them in action, except Burgess, and all he did was get wreckedy Sabo repeatedly. So the following ranking is completely arbitrary.
1: Blackbeard (Duh. GuraGura and YamiYami, Oda knows what else at this point.)
2: Kuzan ( Strong enough to be fleet admiral, and was able to fight 10 days against Akainu with a massive disadvantage in DF's) (Probably not an actual member of BB Pirates)
3: Shiryu ( He's a Swordsman, so he's most likely going to be Zoro's enemy. Therefore 2nd strongest.)
4: Laffitte (He's weird, and that guarantees he's the very baddest of asses.)
5: Jesus Burgess (I suppose he was a big deal. But he's been one shotted by Sabo approximately 20 times.)
6: Van Augur (Okay, at this point i'm just ranking them based on how badass they look. Guess what, Vasco Shot is at the bottom)
7: Sanjuan Wolf (He's big, but that's almost never a decider. See Sanji and Jimbe vs Wadatsumi)
8: Avalo Pizarro
9: Catarina Devon
10: Doc Q
11: Vasco Shot (Told You)