I mean, I personally think that if you flatten the aliens with nukes you should be able to drop archeology teams on the flaming ruins and and get intel/tech that way... not just with ancient ruins.

Again, very good idea, and hard decision to make.
xenoarcheologists, should not be taken as indiana jones kinds of guys brushing sand off some vases. Since this is military unit i assume those are more like combat scientists. Currently there are combat engineers in army and despite the name those are guys keeping the power generator in base working, changing CAN bus in humvee, recovering broken vehicles or armament, setting wifi in barracs or securing antennas and radar instalations. Those are armed (combat thingy in the name) guys, and trained to some extent, but fighting is not their best use, and are not used in that way mostly at all.

in my opinion xenoarcheologists are the science guys that can determine what is worth taking, whenever that rock/rubble/pertruding-in-your-face-barrel-thats-definitively-loaded-with-bad-stuff/writing/vase is worth, and safe  to take with you.

IMO its not necessary bad to add such quality to the xenoarcheologists (especially that those are mostly just standing there most of the time) or it can be done with other unit too, but the issue with that naming stuff, (post by Migi) you are against it just because bad naming (-archeologists stuff in xenoarcheoligists), so there is a good chance that this could be solved just by changing unit name to xenoanalytics.

I would rather see dedicate sensor equipped ground units rather than repurposing the xenoarchaelogists.

As it currently stands, I believe your xenoarch's can help your ground troops in combat by recovering xeno technology from abandoned worlds prior to combat. I know for a fact that I have found missile caches on abandoned alien worlds and have been able to study the missile designs as a result. I am not sure if xenoarch's can recover unit designs, but if they currently cannot, I think this would be a useful improvement and would allow the player to tailor any ground troops to those xeno's in the future.