How stupid to class the Empire together with the Separatists...

Well, I think it's more that both had Darth's who were openly in charge.

For this one: R2-D2: Who knows what secret upgrades he still has in that roomba-like shell. While Wedge only really grew into his own during the Vong crisis. Also, this pilot Wedge needs an astromech to properly fly and those guys would be cheering for R2 anyway...

Admiral Piett: a) He managed to get along and develop a working relationship with Darth Vader b) He lacked the arrogance of Tarkin thus should not make stupid super-villain-like mistakes c) While both were taken out by a single Starfighter in the end, Tarkin died due to ignoring the dangers one posed, Piett died due to a stupid accident that I doubt anyone will ever be able to replicate.