Another option for more AA and better Psyker stuff is taking a small detachment of Daemons, such as 11 Horrors, a Soul Grinder of Nurlge with Phlegm, and either a Tzeench Herald with 2-3 Mastery levels (Divination babyyyyy!) or Be'lakor (expensive but absurdly powerful, and since you're already rockin' the Don it's a bit much). The Grinder is a solid portion of Anti-Air, especially with Divination from the Herald, and can lay down the pain with the Bombardment. The Horrors, meanwhile have a very nice, albeit cheesy, interaction with the Aegis, as going to ground grants them a 2+ cover save, but for them it is re-rollable because all Daemons of Tzeench re-roll saving throws of 1. Plus, they'll grant you an extra 2 Warp Charges since you're taking 11 of them.
If Daemons aint your style, I would really consider giving Aby a Land Raider to travel in with some Termies, just because you need him to get into close combat to make him worth the points, but again, really expensive. You'd also have to drop a Heavy Support choice, but the results can be extremely deadly when used properly. This would also perhaps entail kitting Termies for assault instead.
Otherwise, this list seems pretty solid! You have all the right bases covered, good threats, and versatile troops. However, I do feel your list lacks a major threat to press your advantages gained from popping a vehicle or opening up the opponents defenses. Abaddon in a Land Raider would fix this, or using him to Deep Strike with the Termies, but the second option can be very risky and may not come in at the right time due to the randomness of reserves. Having access to Divination can help this with Scrier's Gaze.