Uh, the AR7 isn't weak because of it's individual capabilities, it's weak because it's one gun. This game is all about switching weapons, and using multiple weapons in one battle. That is the whole reason why it's fires are so diverse, one mid damage projectile, and one rapid fire hit-scan weapon. It has to be somewhat weaker then the rest of the weapons so newbs know it's better to find another gun (see halo), but powerful enough to at least make your oppoent think.
The enforcers were as much weaker from balance perspective then the rest of the guns were, as the AR7 is now, because then, all the other weapons were way stronger. Combos decimated fresh spawns, one direct rocket offed them, and flak also killed in one ammo on either fire (actually it still does). A combo is much less likely to kill a spawn now, unless it's very precicely placed, and a rocket will not kill in one (and that is before accounting for spawnprotection). Flak can be done in one hit, but is much more difficult.
The SG was another reason the AR7 didn't need to be as much of a threat yes, but it would be hard to balance the AR7 vs an LtG/Link, Rox/Mini, or Shock, or any other 2 weapon combo you can think of, so why try? You really can barely think of any weapon in this game as one gun, you have to at least think in pairs, and AR7/SG is enough to survive to a weapon usually.
Next UT will be different with no SG. Hence the Enforcers return. I, though, was more likely even in UT to run IH instead of 1 Enforcer. Most maps were tight enough, you could be moderately effective with it, and it was much more intimidating.