If the 12mm actually landed half of it's shots on anything smaller than a battle tank, it'd be great! That's a flaw of every dual weapon system, along with the fact that the RoF doesn't increase as a result (still not sure how the hell that works out...the dual guns fire at the same rate TOGETHER as a SINGLE one does...shouldn't there be twice as many bullets used in the same amount of time?
).
Problem with the Prowler has to do with comparisons.
1) It's a big, giant target with medium armor. It's common competitors are both shorter and harder to hit, and in the case of the Vanguard do more damage per shot...which really sucks when it's easy for them to land DIRECT hits on you.
2) If you're going into a straight armor battle with full crews, the TR can take a full platoon and field 10 tanks. The NC and VS can both take that same platoon and field 15. Want to place bets on who's going to win that fight?
3) Pretend that they don't take full crews, the NC and VS can drop two tanks from their force and get 4 Reavers and completely devastate the Prowlers that have no way to respond. 4 Reavers > 2 tanks with no ability to counter them.
4) The Prowler, despite being the biggest target, cannot outrun anything. If you get badly damaged, you better pray for support because you're screwed otherwise.
Quick and dirty solutions to the 1v1 imbalance with NC (it's a decent enough tank against the Mag): Swap Armor with Vanguard OR swap speed with Vanguard. The Prowler should be superior to that tank in one of those areas.
Solutions to the 150% crew requirement: Dunno, short of allowing the main gunner to control both if there is no 3rd crewman.