Regarding Dialga counters. Defean lock, no trainers really hurts, and there isn't any counter that easily fit's in.
As Uxie Double Donk creator... I couldn't figure out a solid counter to it, that didn't hurt my core build. Thus with my logic, I chose to pretend Dialga doesn't exist. Thus on my build, it isn't an auto loss, but I hope I can KO there starting lineup, hit on my cyrus initiative to fish out key cards out of there hand. Believe me, if there was a good counter simple counter to this I would do it.
My logic is too push the hard on the first turn all out carpet bomb, without techs that interfer with this. Hope I don't have to play them, and if I do, hope I can carpet bomb on first turn. Once the go Deafen Lock, GG.
The other option is don't be consistent with Shuppet Donk, mix up your deck choices. Shuppet or Uxie donk can work if you avoid the dialga's. I played my Double Donk first day of cities, and left it in the bag for the rest of them. My first game, I first turn TRIPLE Donked my opponent. I did make top cut with it, but I lost to Gastly starts by Gengar opponents. I can't do the TRIPLE donk without being dependent on trainers, can't beat dialga, gengar, spiritomb, if I am dependent on trainers. Shuppet Donk can do a bit better, but it can't consistently double donk.
There are creative "threat cards" such as torchic and multi energy, but a good player can defeat these threats. Swinub can flip for parylyze/sleep. But you need multi, and Poketurn easily defeats this. Again, nothing solid, and it hurts consistency.