WAPADIDM,
I'm just curious, based on on of your questions and rave reviews of Dressel...have you dove with any other operators in Cozumel? If not, I encourage you to try some others out next time and you will see the difference so many people are talking about. I am not saying anything good or bad about Dressel, but if you don't have a frame of reference, you really wouldn't know that you have some other alternatives that I believe you would find more to your liking.
As far as your question above, this depends on the opertor. There are several shops that truly are dedicated to customer service, and along with this includes matching up divers of equal/similar abilities or making accommodations accordingly rather than just filling the boat with whomever comes along. These accommodations may include sending out more than one boat, sending an additional DM on the boat (even with a group of 6), or sending divers up in buddy pairs as they reach the designated psi with the DM's line.