Hi Sumvin.
It is a very solid and very effective team, I can't really rate your team because it seems very correct, but I see a weakness against Thundurus-T, I explain you: even if you possess Mamoswine and you can't come with him on Thundurus-T because you can take a Focus Blast, and then you have nothing for tank his attacks as Hidden power Ice/Thunder or ThunderBolt, Celebi is OHKO by Hidden power after a nasty plot and Rotom is OHKO by Thunder/ThunderBolt after a Nasty Plot, then I see that you are very disadvantaged against Keldeo Spec because even if you have Celebi he cannot do anything, because it does not recover, and he's 2HKO by Hidden power Ice, Rotom is 2HKO by Secret sword and then your team is weak against Toxic Spikes, I suggest you to put Amoonguss on Celebi, Amoongus is a very interesting pokemon for your team, it can cancel the Toxic Spikes, it is a very good counter for Keldeo, and it has its ability (Regenerator), with his ability, he can switch and come after without problem, then now you can sleep a pokemon with Spore, then Amoonguss is a very good counter for Thundurus-T because it can use Spore or 3HKO with Sludge Bomb because it is Not OHKO by Hidden Power Ice.
Tl;dr
I appreciate a lot your Sableye, it can stop many of sweeper with lagging tail, I put a like ^ ^.
Hope I Helped and Good Luck with your Team.