They tend to suicide in CQC (the higher tier you get, the easier this is to do), and they have a very hard time hitting above them. They were also considered (as heavily agreed upon in a thread) as the weapon that requires the most practice to be good with. (the title is currently held by plasma cannons)

I actually made an alt that uses plasma cannons. I personally think that they just need to improve more as the tiers increase. Players seem to not understand where you should use these (they're best in high-cover areas for supporting your team- not killing in the open 1v1)

I would say another characteristic of an overpowered weapon, is one that makes the role of other weapons utterly superfluous. Not in the sense that say a Light Weapon is superior than a Secondary Weapon (After-all, Secondary Weapons are meant to be "lesser" versions of primary weapons), but in the sense that a weapon makes you say "Ppfftt, why on Earth do I want to use those when I have THIS one that can accomplish the same function", ergo, the way Assault Rifles and Scrambler Rifles (to a lesser extent) utterly make Mass Drivers, Laser Rifles, and Heavy Machine Guns (Yes, I included HMG's, in a game where speed is valuable, I can kill mercs just as quickly with an AS or SR without the disadvantages of the HMG).

That to me is also a huge problem of the current Assault rifles, it makes a great many other weapons utterly superfluous. I really do hope they bring the stats of the Chromosome-era Mass Drivers and Laser Rifles (with the Viziam naturally being teaked ), THOSE competed well on par with Assault Rifles, and using different means to do it (MD = Splash Damage, LR = Long Range persistent damage).