Buff or nerf depends on your starting point. If you have a lot of CHD already on your build, then converting ~23% CHC into CHD is not going to be a big increase. If you have a lot of CHC but low CHD the change makes your build output more damage.

If you're like me and have around 43% CHC (20% base and 23% from SMG) and 60% CHD then it is a nerf. 1% CHC for 1% CHD is NOT a fair trade for a vast majority of builds in the game.

On the PvE side, whoever at Massive came up with it, definitely had a stroke of brilliance because it creates balance. Now if you run an SMG you need to balance to get the best out of each stat you want to increase and should be putting more into whichever give them less diminishing returns.

Also they made pulse relevant again, because of two reasons. First, gun balancing will encourage people to move to other weapons, which benefit a lot from a good pulse, making it useful for the whole team. Secondly, even if you're sticking with a SMG, the pulse is now relevant again.

Good change regardless of buff or nerf.