Since D. Gallade is physical, I would swap Ice Beam for Livewire which is a good hazard move to have and switch Aerial Ace to Drain Punch (better coverage and gives some recovery). Ice Punch should get replaced by Icicle Crash later.
For D. Haxorus I would consider replacing either Aqua Tail or Heavy Slam for Aqua Jet or Bullet Punch, respectively. Having at least one priority move would help D. Haxorus avoid taking further damage when opponent has just a bit of life left.
Rotom I would replace with a more useful pokemon. Most go for Wash Rotom as it is the strongest form defensively/offensively but since you already have a water type in D. Haxorus and an electric type in D. Gallade, and the other Rotom forms are not that great, it would be best to replace it for another pokemon. D. Bisharp is worth considering here as you don’t have any flying/fighting types on team and those aren’t covered by Mega Eevee, but you could go with just about anything that gives more offensive/defensive diversity to team.
There’s a number of strong fire type pokemon you can choose to replace Rapidash. Delta Chandelure and Delta Vespiquen are both strong options (although you do already have a steel and fairy type in D. Haxorus and D. Roserade). You could also consider Blaziken, Talonflame, Volcarona (once you’re further along to be able to evolve it), and regular Chandelure.
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