I just lost an assault specialist because I didn't realize two enemies were on overwatch. Was there something I should have noticed that would have told me they were on overwatch?
I'm fairly early into the game but if an enemy is in view during their turn you can see when they go on overwatch. It pops up on the screen that the enemy has entered overwatch. I assume this is only for enemies in your view and that it doesn't constantly say it over their head thus forcing you to remember. I'll have to check somehow.
UPDATE: After playing the game for a while I've seen a lot of enemies go into overwatch. There is no way to tell they are in overwatch until they fire unless you see them. You need to remember what enemies are doing what.