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Really? You're going to have Anti-Tank squads?
I never use them because they really don't have the staying power that an IG needs for his heavy weapons. My Advice is to max out your 10 man squads. They can take more damage before they go down and they provide a much less juicy target for your enemy's fire.
Of course my advice is coming from the way I play my army like a Russian General which is basically to say 'Not One step back" and throw my men into needlessly risky situations like charging the Space Marine assualt troops. and hoping that the enemy trips over the dead bodies of my men and break their necks.

Captain Al Rahem.

The Tallarn will maybe get a new character with the third Imperial Armour installment of Forge World (The Taros Campaign). As for the Valhallans, if GW ever plans on releasing the fabled greatcoat plastics, who knows?

While the support squads can be easy targets, their combined weapons fire can be decisive. Think of it, three lascannons along with the sharpshooters doctrine. Same with three autocannons, just think of the damage they can do.

I''d go for the three lascannon setup, works better. I try to avoid mixing the weapons in support squads, meaning that you wont waste shots on targets out of reach or harm.

The commander should decide for him/herself what is best for the army. I myself field four support squads: mortar, special weapons support with three sniper rifles, an anti-tank support squad with three lascannons and sharpshooters and a fire support squad with three autocannons and sharpshooters.

Weapons of the same type that are grouped together are more effective then mixing them up.

Most people will say that the Sharpshooters doctrine is a waste but when applied to support squads with expensive heavy weapons, it's bound to earn it's worth back, as the ability to re-roll 1's for lascannons and autocannons can mean alot.

Infantry squads with heavy weapons is also something of a must. In my 2.000 points army I field two three squad infantry platoons. Both platoons have the same squad structure: 1st squad with a flamer (For moving out or counter-assaults), 2nd squad with a grenade launcher and heavy bolter and 3rd squad with a grenade launcher and missile launcher.

Command squads can be tailored to fit multiple tasks. My second platoon command has a basic JO with Iron Discipline and bolt pistol. The rest is divided in using a grenade launcher and missile launcher. My first platoon command squad has a basic JO with carapace, bolt pistol, power weapon and Iron Discipline, a medic with lasgun and three plasma gun toting guardsmen. Perfect for zapping high armour foes.

You do remember that for every AF squad you must first field an infantry platoon, right?

Gotta admit I'm not a big fan of your list. It's way way to tank heavy and your squads should have heavy weapons in them not just special weapons.
Next take off the lascannons from the Leman Russes. They never really come into play and they are going to come into direct conflict with the heavy bolters. Do you go for the single shot against the armor 12 of the 7 shots against the infantry? I mean one person in that squad is going to be reduced to a smoldering crater but you can do more damage to the squad using a heavy bolter.
Also I don't think you're ever going to find the stormtroopers worth it. Sure they have BS 4 but it's with a Str 3 weapon then of course the AP isn't going to pierce that much armor.

Ah I see that now
Srry bout that.
I reccomend buying a couple more squads of men because right now you don't have enough troops to make a decent IG army. I'd buy as many squads as I could.