wow, that a fairly formidable squad!
you need high def (sith, Exar and ulic both having 23s, and in cover, having 27, but veeeery pricey.) u could also go with darth sidious sith master, a sith heavy assault droid (for pawning, a double twin at + 10 to attack, essentially giving the heavy 8 attacks after it activation) and an HK-50 (heavy damage output, decent def, and very pawnable.) build around those and give it a shot.

i dont doubt droids at all, ive gotten my arse kicked by many a droid, but high HP allows you to live longer, especially those 2 (exar and ulic beatsticks), but my success rate with those 2 against a similar army was 50/50.
now my mandalorians on the other hand, on an Ulic squad with HoloSid, will eat droid armies for lunch. mind you, im talking a 250 pt. squad.
as far as Vassal goes, i still cant figure the darn thing out. i wouldnt mind gettin creamed a few times, if i could only figure it out.

a rebel squad with Verpines, that sounds plausible...
matter of fact, a reb commando strike leader, some reb commandos, a reb leader, 2 verpines, 2 mouse droids and gen rieekan.
they cant attack you from a distance while in cover, they have to be adjacent. and even if you didnt have cover, youd get Rieekans evade, and his twin for offense. with the verpines jolt, it would be droid activation city. playing it the right way is key though, because if you just throw yerself at him, he will pick them off one by one. but there isnt anything better then super stealth against a droid army.

errrr,,,
that is a problem.
work some kind of squad that has super stealth, like moff nyna calixte with some emperors shadow guards and mystral shadow guards (if you have them), but then you are looking at a straight beatstick squad.....hmmmmm.
toss in a Bith and Twileck BS vigo with the IE thrawn, so all can have opportunist maybe?

i was thinking a merc squad with Nym included, just for the extra att value, and the merc commander also gives deadeye, giving those same chiss mercs 40 dam per extra attack. but my only problem with the mercs, is their lack of movement while in LoS with enemies, and their Def. the upside is their range of hp, mostly a 40.
TechDog has the right idea....

The only problem i have with that is he is i cant use opportunist on his main units until most of my heavy hitters have already attacked. And the other is his IG-86es have quad attack when they dont move and have the ability to hit for 120 dmg on an activated opponent at a +15 or so attack(i dont remember their attack with all the bonuses but its high) the mercs have a low HP so he could kill 2 of them with only 1 IG-86.

The Mercs do have low DV, but if you can force him to go first it will give them someone to hit. And, you have low level guys to move first as well, the Nogrhi, the Stormtoopers, you can out wait him just as much as he can out wait you. Especially if he is going to keep his commanders in a room. Don't worry about them, they can't attack you. The IG86's only have 60HPs, so you can wipe them out in a single round with the Chiss, thats 4 shots at them. And the Gotals and the Merc commanders, you can overwhelm him, you just have to out wait him, just cause you can rush in, doesn't mean you have to with this team. Or, if you have Admiral Ozzel you can add him in for the 11pt stormtrooper and only activate one character at a time and play his game.

His Team is good, but it can be taken down.

One thing to make sure you're clear on - the Geonosian Overseer doesn't have a commander effect, so Double Attack isn't transmitted through the mouse droids. If the overseer is locked in the back room he's useless.

He really only has 3 main damage dealers - the lancer and 2 IG-86s. So you can build to take them out in one activation. A bunch of Ion Guns with Twin Attack could go a long way.

Omnus, something to point out, with strafe he does not have to attack each enemy he flies over, the description says: As this character moves, it can attack each enemy whose space it enters. so because it says can and not must that gives him the option not to attack.

I think Bane is a monster and he can be a wonderful counter to almost anything if you can get him in close. If you want a good counter to the Lancer, try Kel Dor Bounty Hunters. The lancer has to attack Melee, if he takes out a Bounty Hunter he will take 40 damage for doing so. They also have excellent AV and stealth. 3 of those guys for 13pts each can be a real pain to deal with for a melee heavy army.

I like the mercs cause they can get shots off on many targets and do big damage for a very cheap cost. Just find the right commander to go with them, GMY is a good one, GOWk(of course he was), Grand Admiral Thrawn, and anyone who can up their AV or DV. Expect to lose one or three, but if they each get off one Furious assault they are worth their points.

I know you don't plat rebels, but I think they are the best for countering droids, I have a counter for my friends Crab Droid army and its all about the rebels. I think the Sith have the pieces to make a great droid counter team, but I am not sure what pieces you have. I will come up with one I think would be great and post it tomorrow.

Good luck and have fun.