Nukeproof's comment is the one out of line here. The Inf team have always been dedicated to realism, with gameplay coming in a meagre second. Of course there's a limit as to how far you can go, but that's no excuse not to push towards that limit.
The AT-4 was simply implemented to give an example of what could be done for an anti-armour objective. Heck, they included the UT rocket launcher as an example of a weapon, and nobody's complaining. However, neither of these are implemented in a realistic manner, neither are meant to be used against infantry, and as such neither should have a place in the common soldier's loadout.