The stuff that has been circling around is
1. IG command section with Lascannon.
Pros: Cheap, total of 65 points for all of it. Lascannon
Cons: BS3, Only one squad in your average army since you need a Sister HQ and Retiniue.
Only 5 man with Flakarmor is really vulnerable.
2. IG squad with Lascannon.
Pros: Lascannon, takes more beating than most of your other options.
Cons: A 10 man squad for just 1 lascannon? Expensive 90 points for a measly BS3 lascannon and shockabsorber.
Only one squad in your average army since you need a Sister HQ and Retiniue.
3. IG veteran squad
Pros: BS4 Lascannon.
Cons: Costs alot, is very vulnerable with only 5 men and very expensive with 10.
Only one squad in your average army since you need a Sister HQ and Retiniue.
4. Redemptionists with Autocannons and redemptor priest.
Pros: Can take alot of beating, are available in large groups as they are standard troop choices, cannot be broken before the priest is dead. Acts of Faith.
Cons: Can't touch AV14 viechles.
5. Exorcist Tank
Pros: EXTREMELY powerful weapon. The exorcist launcher BEATS the Eldar Pulselaser in terms of sheer firepower..even if it's not AP2. Can Move and fire.
Cons: Expensive, Vulnerable and won't surivive long if the enemy knows what it is.
That is what you have for long range AT power.
And you have no lack for Short range anti-tank powers as you have Dominions and Seraphim plus a WHOLE lot of meltaguns.