I have all the commandos at 5 and to be honest, the problem is lack of weapon variety. The commandos themselves are pretty balanced to my mind, the problem is that only the min actually has two weapons to use.

Minmatar can use either a combat rifle and a mass driver or two combat rifles. The first compensates well for the commando's lack of a grenade slot gives good variety to the role. The second compensates for the combat rifles low magazine and ammo count, easily its biggest drawback.

Gallente can use two AR's but really you aren't gaining much from using them. Clips are high already and with the lowest range you're still functioning within a very limited role. Plasma cannon is pointless since its a OHK already, and the gallente is too slow to use shotgun effectively. Besides, the 10% bonus doesn't make a lot of difference in the shotgun kill time anyway.

The charge time on the Rail rifle makes stacking two of them on the Caldari Commando a pointless exercise. A sniper rifle is handy and I use this commando a lot when countersniping but overall it's a very limited role.

Amarr commando to me is the oddball of the lot. Laser rifle and Scrambler rifle have too similar ranges. Stacking them seems redundant or at the very least to make a very minor difference. Stacking dual Scrambler rifles is a better combination to my mind because it compensates for overheat, but with a scrambler rilfle you really need speed to strafe with a target and as the slowest commando, the Amarr just doesn't have that.