As a Rebel, so far I encountered one Imp base with the guard reserve, and it was the factory with the speeder. It was probably a level 1 (I'd assume at this point anyway), since it spawned 1 at the start, and only 1 more throughout the entire battle from each factory (though I destroyed the one factory pretty quickly). Heavy Reb + Med destroyed them so quickly it didn't even make a difference. They literally popped up and were removed immediately. Especially because at the start of the battle they appear, zoom out at me, and I can just swarm right around them at the get-go.
As Imp, I've faced two bases so far with the Skiffs, and they actually made it a little harder. The first one, not being ready for it, quickly destroyed my eATAT on Tat. The second on I think either Dando or Tako I was more prepared for, and gave my ATCT some protection.