If a tech win is close enough, I'd even ride out a stomping by an AI...I don't foresee the AI being any different. You may need to try and fast-buy enough troop ships and target their high research planets to try and cripple their progress on the tech. However, complete annihilation of the Dregin will need to be done so that this doesn't happen again in 3 weeks.
I was once trying to race the Alterains to the finish line. They were researching Tech Victory and I was going for Ascension in TA. My spies weren't cutting it and I ended up reloading my game a few times until I found a way to beat them by a few weeks. It involved a ton of quick buys and practically emptying my planets to try and take down their research planets. I turned a game that was going to be lost by 15 weeks into a win by even less.
So that said, unless you are on the verge of winning, you will need to decimate the Dregin. I think the only time they hop away from a tech is in the plague/disease events.