Add natures to what each mon has please. It makes it easier to rate if we know if Heatran has a Timid nature, where it outspeeds and beats Max Speed MScizor, or if it's running Modest, where it dies to a +1 or +2 Superpower.
Also, you have a very HUGE Manaphy and Keldeo weakness. Manaphy just 6-0's you if it has Energy Ball and Scald, whereas Keldeo can beat 5/6 of your members, and thus has the remaining 5 of his members to just worry about only wearing down Gastrodon. This can be fixed by removing Heatran altogether, as it legitimately helps you deal with nothing bar Scizor, and /or removing a Sand Stream user. There are better mons than Tyranitar that can occupy your mega slot, as well as there being better support mons MTTar can have than hippo, who shares many common weaknesses. Gliscor can potentially be removed as well for something else with a ground immunity, such as Rotom-W for safe pivoting and a solid Flying spam check, or SDef Talonflame, a great check to fighting Megas (MMedicham, MLopunny), who heavily threaten TTar (if you plan to keep him).