In ideal Dialga setup, you get your 1st Dialga with Energy Gain, then the second one with Unown G. With Dialga and Cyrus in starting hand, this is very propable scenario (Cyrus for Cyrus, Metal and Gain, next turn Cyrus for Poketurn, Roseanne and Metal, next turn Roseanne for Dialga and G).
After that, no Amnesia or anything can stop the Dialga. Even before that, you will have to get the Amnesia out at your turn 1. Plus they have level up to get a rid of the status.
Uxie MT is one of the wild ideas, but I don't think it has any other uses than try to get a turn in deafen build. Palkia Lv.X is my choice, but it needs some skills and water+warp energies to run it.
Perhaps we will have to admit that solo Rampa just plain loses to Dialga G builds. That doesn't make it a bad deck, just a bad metagame choice. If you figure out a working tech against the Deafen lock, that would propably be some G-pokémon that does not get damage from the poison and can damage Dialgas faster than Dialgas damage them, but if it's just a tech, it loses to G engine as a whole deck.