This post is indeed posing a very intriguing question about the DMR and the BR.
Personally I preferred the BR to the DMR because achieving a four shot took a lot more skill since it was harder to land shots, what with the having to lead shots and some people's excellent strafing ability.
It's a possibility that the BR could have a lot more bloom than the DMR because it takes less shots to kill someone. They could just slow down the fire rate of the BR to keep it balanced as well. As far as the four shot to the head vs. four shots to the body and one shot to the head, I think that they would adapt the same design to the BR, being that it could take three shots to the body and one to the head, seeing as how they might not bring back bleedthrough. This of course means that the BR would take down shields in three shots... This could be overpowered though.
I guess we'll just have to wait and see exactly what 343i does with Halo 4.