Spectre - I hate damn things, they are immune to overwatch
They are not, I took one of them down through overwatch fire. They do however have a low chance of getting hit in their gassious form.
Avatar could be mitigated better, with new options to reduce avatar counter common situations from XCom2, when you lose just because you cannot reach the factory due to contacts limit, supply limit etc., is almost impossible.
Well you have leads for that. If you can obtain a lead to site, you can do a mission without making contact with the region.
Covert actions could reduce the counter and give you time to reach the facility.
Sabotage covert missions do just that. They remove bars from the avatar project counter.