In Kenobi's Command (rebel), we've had a mixed experience. The first few wars were hopeless mismatches in the Empire's favour. For the next 20 wars, they were winnable, even though the Empire always had higher HQ bases and more of them. The outposts make a huge difference, and HQ level isn't always reflected across a base.
Usually our war requests are met in minutes. The last few have taken hours. When we've waited hours, we end up against a much tougher Empire base. I think the devs are monitoring those with good win-loss rates and giving tougher opponents.
In our current squad war, we have:
1 10 (only the HQ is 10, the new buildings/turrets are still at v low levels),
6 8s, and
some 7s and 6s.
5 10s (each slightly more advanced than our 1 10)
a 6 and a 5
The outposts are
Dandoran (troop health boost)
Takodana (troop damage boost)
Yavin (starship boost)
The outposts are more likely to be useful to us than them, but only if we have them and can keep them. They have 7 bases that should easily re-take level 9 outposts, to our 3. This is a complete mismatch in the Empire's favour.