Since Seekers, Disciples, and Illums are clearly OP (and Halcyons are a bit, but at least they are tolerable), you can expect them to be nerfed/fixed (in case of Illum) in the next patch.
LOL. First question. who told you there would ever be another patch? Second question. Even if there is, who told you these things would be nerfed?
So... I played a 4p locked FFA with random race (ended up Vasari) and was immediatly rushed by the nearby advent player with dual halcyon's. I did survive his initial attacks with my Egg, repair bays, turrents(upgraded), Starbase and fighter/health upgrades and scared him away. I even managed to get a comparable fleet built of carriers and assailants and some sentinals due to aggressive control of neutral extractors.
If you were able to get all of that up, doesn't sounds like much of a rush. I guess the guy took his time. When Howthe? rushed me the other day, his Halyon was at my HW before my scout was at his (YES I SCOUTED CORRECTLY).
Would mass vasari sentinals have worked better against a heavy illum with dual halcyon fleet.
Sentinals at least last longer than assailants because they are tough. The problem is, you simply can't churn out the masses of sentinals needed in time. At minimum you will need twice as many sentinals as he has illums to give him any pause. If he has 40 illums you'll need 80 sentinals (that's a lot). You have to build them by the tonnage, they seem to take forever to build, take a lot of supply/cost, etc. You'll never have enough sentinals in a rush situation - forget about that. Even worse, he sees you preparing sentinals, he may not even go illums. He may just keep mashing the "build disciple" button.
Assailants are good at hitting the halcyons but it seemed when I tried to engage the Illums it just didn't have that big an impact.
Do NOT build assailants to counter advent. For one thing, illums just shred assailants. For another thing, he could just seeker you to death.
Does the charged damage upgrade help any with assailants or sentinals?
Helps with assailants, but you can't tech that in a rush situation - impossible. Works with sentinals ONLY AGAINST STRIKECRAFT, so it won't help you there vs. illums or anything else.
Unfortunately, my Assailants just look like popcorn against illums IMO.
Assailants totally suck against illums, big-time. Actually, these days I'm starting to think assailants suck period. When I was still playing vasari, I had totally quit using them at all. I pushed SB's, and tried to back them up with support (flak, carriers, etc).