Ahem. Here is the equation that has unfortunately had to be reiterated many times over:
Return (102) + Return (102) = 204 total damage over two turns.
Hyper Beam (150) + recharge turn (0) = 150 total damage over two turns.
Also, you can't switch out during the recharge turn, allowing for the opponent to either make a switch of their own or set up on you.
It doesn't really matter if your team has Mence's weaknesses covered, since a little redundancy concerning move types never hurt anyone. Salamence is best with those moves, so use them. Oh, and Hydro Pump and Crunch aren't TM's. Salamence learns the former through breeding and the latter through level up.