Different factions have different tricks, things that bypass saves all together is good, my personal favourite for the Separatists to counter specifically soresu/evade is this:
http://www.bloomilk.com/Squad/163207/-lets-try-missing-for-once----how-to-counter-ranged-defensive-abilities-powers---"Let's try missing for once." (How to counter ranged defensive abilities/powers)--
55 Sev'rance Tann
27 Lobot
96 Octuptarra Combat Droid x4
19 BX Commando Droid Spotter
3 Ugnaught Demolitionist
Preferred Reinforcements:
(Lobot) 20 Blizz
(200pts. 9 activations)
You get 4-12 shots a round, all with splash 20, and you actually want to miss, if you do then they essentially get hit by a missiles and they end up having to spend force points to reroll saves instead of stacking the usual soresu/evade.
The Dwarf Spider Droid's Advanced missiles are also a good combo as it is a save of 16 or 12 for those with +4 to saves.
Alternatively for direct damage you have self-destruct, flamethrower, the aforementioned blast bug and the plethora of fort powers my favourite being lightning.