I agree with what you said. I'll take your analogy a step further, if you don't mind. The AR is, like you said, duct tape. The carbine is like duct tape that doesn't stick most of the time. I can count on the AR to get the job done in CQ, however, I can't count on the carbine in any situation.
I'm sorry, I didn't clarify. Let me start out with this- the DMR is an all-purpose weapon, the BR is useful at mid range, the LR is useful at mid-long range, but the carbine's use is limited to close range, in most cases. Therefore, the carbine would be the only weapon that would be able to compete with short-range BS weapons such as the boltshot, but because the carbine is so underpowered, it simply fails. Giving the Carbine a buff would be a very simple fix, but I doubt that there will be a fix unless the majority of the community feels it needs it.