Totally was meant to get to this earlier but never got around to it, so yeaaah posting move suggestions now! Considering your levels, my comments should still be fine & apply thanks to the move relearner, lol.
Okay so for Sceptile, Leaf Blade and Earthquake are okay IF you're using Swords Dance. You'll need to get that from the move relearner, but considering the fact that its special stat is much higher, you'll definitely benefit from the Swords Dance boost - just team that up with life Orb and you'll be good, if not, then leftovers will be good. Go for Rock Slide also so you can cover fire types, etc and EQ for steels you can't really do much else to otherwisel. Plus Solarbeam is a two-turn attack and unless you have a sun team then generally it doesn't fit on any Pokemon.
For Rayquaza, consider Dragon Dance > Fly since you won't be flying around much post-game and boosting your stats is better than having a filler move.
On Metagross, Hyperbeam is a bad attack, since you end up wasting a turn, and it isn't STAB so it doesn't do much. If you wanna swap things around, go for Agility so you don't lose speed @ Hammer Arm, and replace Hammer Arm with Earthquake, which covers pretty much the same things.
On Haxorus, go for Dragon Dance to boost your stats, Focus Blast and Guillotine don't really help, mainly because Brick Break is a much more effective attack since it can break screens and is physical compared to special - aka Focus Blast which has worse accuracy. Giga Impact is as bad as Hyper Beam, leaving you immobile for one turn. Go for Earthquake and X-Scissor for coverage over other things such as steels/psychic types pretty much.
On Hydreigon, Hyper Voice doesn't really do much since you'd much rather all-out attack. Draco Meteor or Dragon Pulse are more effective for it since the power is pretty good + Dark Pulse, so you have both STABs covered.
Aaand that's about all! Need to relearn a few moves a bit though ;x