I felt that the MSBS, even in it's original form was a mediocre weapon. As a burst AR I felt it had a low RoF cap and it's recoil was a little high. I say this as someone who use got the Type 95 and M16 gold every prestige often and early. To me, the MSBS didn't hold a candle to those weapons even pre-patched. It wasn't a useless gun by any standard, but it's long range performance was "meh" at best.
Post-patch it's easily the weakest AR and the only thing it's good at is being a pain and the ass a long range engagements. I see more players using the burst attachment on full-autos and MRs than I do the MSBS.
Fun fact: There are multiple ARs that, with the burst attachment have less recoil and more damage than the MSBS.
It's nerf was completely unnecessary and I could see there being good arguments for buffing it even, though it was perfectly fine in it's original state.
What I think causes so much outrage is the fact that a burst weapon takes one pull of the trigger. In the minds of someone that died they see this and, in their own delusional thinking, feel that it's the same as being OHK. They don't realize that it's only a one-burst-kill if every round lands which holds true with most of the ARs in this game. 3 hits-to-kill is max damage for nearly every AR in the game. Since the MSBS is burst fire weapon, has moderate recoil, and lower RoF it's damage is more than an equal trade-off.