Dark Pulse doesn't let Thundurus hit anything noteworthy; HP Ice lets it hit Gliscor and Therian Landorus; HP Flying gives it a secondary STAB:
-Nasty Plot
-Thunderbolt
-Hidden Power (Ice/Flying)
-Thunder Wave/Focus Blast/Substitute
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb/Leftovers
Ability: Prankster
if Keldeo is using Calm Mind, it should use Substitute alongside its STABs to make boosting easier. Secret Sword is the preferred Fighting STAB, as it lets Keldeo bypass special walls like Chansey. Scald is also preferred because this Keldeo aims to stick around:
-Calm Mind
-Scald
-Secret Sword
-Substitute
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Leftovers
You're wasting away Mega Metagross' very good Speed, to be honest. 110 is very good. Change the nature to Jolly and the EV spread to 252 Atk/4 Def/252 Spe.
Have Latios as the Defogger of the team; the only non-Mega set Scizor should run is Choice Band:
-Draco Meteor
-Psyshock
-Hidden Power (Fire)/Surf/Earthquake
-Defog
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Wash Rotom runs 44 Speed EVs to outspeed the odd Jolly Azumarill. Also, Wash Rotom gets worn down fast without any form of recovery, so Pain Split should go over Foul Play.