He send Kuzan during the war in wano, he didn't know that BM was absent.[/B]
You saw what Aokiji did with Cracker, no commander except Katakuri gonna even match up with Kuzan and even Kata would lose.
The gap between a Top Tier like Teach,Aokiji and Big Mom and firstmates are to large(except Ben Beckman).
Teach don't need to fear anyone, we saw what he did with Law crew just with 3 Crew members...
Teach crew is capable to split up into 3 groups, each of them have their own story:
- Teach,Burgess,Van Augar and Doc winning over Law and his crew
-Kuzan,Shiryuu,Vasco,San Wolf and Pizzaro winning over Garp and Navy
-Devon and Lafitte in egghead arc.
The crew is so balanced that they can keep up in multiple fronts. Teach crew is really strong and with Kuzan the strongest Yonkou crew.
Teach with Kuzan is like Whitebeard with Oden or Roger with Ray, two top tiers in one crew are very op.