I've already sent a PM to one of the admins about it but I'll post here anyway.
I think that M26 DART should be on the infantry ban list. After the latest patch it's currently bugged/glitched when the main gun is equipped with Underslug+heavy Barrel - the range of the DART while ADSing increases greatly and it's easy to OHK people at mid+ range, not to mention CQC. Currently not many people know about it so it's still a relatively rare view on public servers but in cbs good and organised players will definitely exploit this. We already have a kind of a spray&pray game going, usage of DART would make infantry-heavy maps a nightmare.
For the DART being OP just head over to EAUK or Symthic forums - there are a couple of topics where people agree on the matter that this attachment is clearly OP. It's role is to be weaker in CQC than MASS and weaker in long range combat than slugs, something in the middle. But at the moment it's stronger than MASS in CQC and hella better than slugs at long range. Here's a YT video showing just what you can do with it - pay in mind that a lot of these kills are made WITHOUT ADS - if the person shooting was to aim down his sight it would be even more effective (HB glitch kicks in when aimed).
There are multiple opinions about this issue in general.
The only thing all players can agree on, that the flechette (DART) ammo with a heavy barel combo is beyond bugged.
But from what i gathered it affects the other rounds as well, so we'll probably bann the whole M26 MASS weapon system until DICE fixes it;
- The frag round is already prohibited by the current ruleset.
- Buck and Slug rounds; some claims its bugged as well, others don't.