I won a domination victory as ARC on turn 138 at Vostok difficulty on a Duel map, but didn't get any of the Steam achievements (I should have gotten Chief Extraterrestrial Officer, Pojexali, Resistance is Futile, Aim to Misbehave, and That New Planet Smell).
The achievement issue may be a Steam bug, or it may be due to the method I used to win - I staged a coup in the opponent's capital with a spy.
Perhaps a quick fix for the contact victory would be to either require all 3 sources of the Signal (no expeditions saving you a ton of turns), or just having the expeditions that would yield the Signal just give you progress towards one of the relevant techs? It would keep it from being too devastating.
Pure Cheese: Turn 48 Domination on a Duel Map. Kozlov, Scientists, Clinic, 100 Energy. Elodie landed late.
Just need Affinity 2, 1 Marine, 3 Gunners. (I built 4, but it didn't really slow me down since the bottleneck allowed it to catch up.) Got Affinity 1 with the free Tech, the other with Cultural Burden. Had to go around a giant Canyon/Mountain range and through a 1 tile bottleneck in the Hills/Forest next to a Nest. Siege Worms also slowed me down a few turns. Scientists + Clinic was overkill on the tech rate. So swap in Machinery or Engineers.
A direct path between capitals and/or a Progenitor Ruins Affinity could speed things up a lot. I'd think turn 30-35ish is possible with a Gunner rush on the perfect map/pops.
Not sure if you can do it with just Marines. Something to try.
It's probably possible to change that around in the game-logic that you are disqualified from finding signal fragments in ruins after you found the first one. That forces you to get the other piece from elsewhere - and then it's more of a tech web design issue and has more to do with the general pacing of the game (the very short "mid-game" section).
It's kind of hard for me to understand how people are getting contact victories so quickly. What is everyone doing, spamming explorers like crazy to find the two pieces?