Here are my suggestsions for each pokemon
Serperior-You don't need that many grass moves. He needs different moves to deal with different pokemon. If he has Contrary, Leaf storm is usually the way to go. If not, then have just Leaf Blade. Leech seed, light screen, or reflect are good for support moves. glare, dragon tail,safeguard and Swords dance are good for strategies, crippling, and setting up. hidden power or Pursuit, make for good sweeping moves (hidden power rock or fire go great with contrary+leaf storm).
Ampharos-He's completely screwed against ground and/or steel types, so perhaps have a good hidden power (if possible) so you don't have to split your EVs for focus punch and for thunderbolt. Thunder wave can work wonders for slowing down things and giving him a chance to attack. (not to mention give him a chance to set up substitute while they're fully paralyzed.)
Briavary-Personally, I prefer sheer force or defiant on this guy. If this is for in game, then fly is fine. But if not, then it could use a different move. Superpower already covers Rock and Ice, so having rock slide for coverage isn't a necessity. U-Turn or Shadow Claw make for some pretty surprising moves. It can get STAB return, so don't rule that out. Tailwind makes a good support move; it would work great with the slow Ampharos.
Krookodile-He has very good attack, so there's not much point in foul play. Perhaps have fire fang to have a bit more type coverage (it deals with three weaknesses: ice, bug, and grass) Outrage is really only needed in OU, where most of the dragons are. Thunderfang or sShadow Claw can be some good sweeping moves.
Haxorus-no need for two dragon moves. Outrage is the more commonly used one though it locks you in. X-scissor, Shadow Claw, and Brick Break, can all be good replacements. Swords dance or Dragon dance is almost always used on him. The seldom seen reversal can also do pretty well on him. Drop Dragon claw and guillotine and replace them with Dragon/Swords dance and one of the sweeping moves.
As for the legendaries, just be aware that using these guys competitively means you'll have to go against teams of all legendary pokemon. If you battle with tiers, then your pokemon are in several different tiers. I'd select different pokemon so they're all in one tier and you'll be able to battle in a stable environment.