I'm gonna divide this into sections. Each section is a different aspect of your team.
Typing
The typing on this team is pretty bad. You have a x2 weakness to rock, x4 weakness to ghost, x2 weakness to water and a x4 weakness to dark. You need to make sure you cover Mega charizard's weaknesses, and you didn't.
Synergy
Honestly these pokemon don't work very well together. You have 4 walls/tanks, no scout, no pivot and not the best sweepers tbh.
Movesets
Charizard: I have no idea why earthquake is there. It can be a mixed sweeper, but yours has no attack EV's and shouldn't have earthquake on it. Run Fire blast over flamethrower. Switch Earthquake out for either roost or dragon pulse. Also switch dragon pulse out for focus blast.
Starmie: Starmie is fine, it's not the best pokemon for OU, there are much better sweepers that can help your typing, but if you are going to use starmie then this set is fine.
Ferrothorn: I personally like stealth rocks over protect. Stealth rocks helps with a lot of pokemon and it can win you games, I've never seen protect win a game on ferrothorn.
Avalugg: It's in NU for a reason. It can be a defense wall, but that's all. It can't sweep, it isn't really viable at all for OU.
Rhyperior: I get what your trying to do, set up Trick Room and sweep with rhyperior. That doesn't work very well and this isn't the moveset you want for that. Stone edge or rock blast over rock slide, Ice punch is good, earthquake is good, but protect is for wall/tank rhyperior's. You want to switch that to probably Megahorn.
Dusknoir: What are you trying to do here? You seem unsure if it's a sweeper with TR or priority moves. Honestly use this as either a wall that sets up TR for rhyperior or as a sweeper that sets up TR for rhyperior.
Well, there is a number of things wrong about the team. You seem unsure about what some of the roles of certain pokemon are. The typing on this team hurts it too.
Hope this helps!
