No, it's likely much, much bigger. I reckon Straw hats is an exceedingly strange crew as far as pirates go. They have absolutely no cannon fodder members like all the other gangs. In fact, they have subordinates who ought to be captains themselves, like we already heard way back during the Enies Lobby arc. I imagine in most crews the captain is a lot more powerful than the rest. Then there's a couple of lieutenants, but that's almost it as far as real fighters are considered. Straw hats have a super class captain, a vice-captain (if you can call Zoro that as the second oldest member) who's also a real monster and easily captain class even in the New world. Sanji probably isn't that far behind. The rest could serve in the role of a lieutenant no problem. This is talking about fighting capability, naturally, because considering more diverse skills they are peerless.