As for the moves we know that it gets that make contact:
Crunch (106-ish BP after boost)
Iron Head (106-ish BP after boost)
Aerial Ace (80 BP after boost)
The Fangs (86-ish BP after boost)
Dragon Claw (106-ish BP after Boost)
Aqua Tail (119-ish BP after boost)(once pokebank comes out)
It has good power and coverage with these moves as well as its 135 base Attack. Let's not forget about its fantastic speed and respectable bulk that allows it to take a priority attack or two. I'm not sure what's so underwhelming or useless about that.
I think the underwhelming part comes not getting good TC+Stab the way ZardX does (for example). Where it to have at least Acrobatics or actually get Bravebird would be great. On the other side the only contact Rock move (i can think of) is HeadSmash which does heavy recoil. Sure the moves you listed above work but overall you are getting the same boost you would if you were running Banded or something (which would have close to similar dmg output). Its like Tyrantrum getting StrongJaw but no STAB moves to abuse SJ (though the boost is equivalent to stab). Which is why most will seitch to Rockhead Tyrant when released.
I agree the speed and power is great but had Megadactyl kept something like Rockhead, heck give it Moldbreaker and rename ToughClaws to ToughFind for MegaGyra it could be better