My reply to bloom is as follows. Would the DMR become overpowered? Probably not. The DMR gets spammed at close/mid ranges anyway, bloom or no bloom it's going to happen. However I can see how the DMR could be unbalanced. I think a good solution might be to decrease rate of fire. Not a major decrease as the rate of fire on the DMR now isn't that high. I would say reduce it maybe .10 seconds per shot fired. Seeing as how the DMR is a 5 shot weapon when done perfectly, that would add at least .5 seconds to kill times. This might not seem like a big increase to some; however, I think it could work.
Personally I think it needs to be looked at in a comparable fashion. Compare DMR to BR, as long as the DMR doesn't become more powerful than the BR I would not consider it overpowered. I say this in relation to the Halo 2 BR in fact. Some say the Halo 2 BR was overpowered. So if we can keep the DMR's power under Halo 2 BR, then there should be no cause for concern.
I'm not using this post as an arguement against either weapon, I'm meerly trying to offer a solution. I personally don't like bloom, but keeping/removing the bloom mechanic is not up to me. But hopefully I have offered a possible solution to the DMR unbalanced issue, if bloom were to be removed.