So right now the GCD cap in bloodlust gets reduced from 1second to 0.7 seconds. It seems that the majority of people think that this is a bug. Although some rogues etc disagree.
The problem with there disagreements is that the GCD cap was introduced in patch 2.4 (Sunwell), so before then Bloodlust almost certainly did effect their GCD, which is likely what they remember. Then in the next major content patch after (Wotlk Prepatch) the GCD was lowered to 0.75seconds, making Bloodlust effect their GCD again.
Assuming that this is a bug, leaving it in will change a few things. Firstly Rogues, and Feral Druids will have lower GCD’s in bloodlust, as they did for the vast majority of TBC.
The other class to benefit will be arcane mages, but not until phase 6. Arcane mages require by far the least amount of haste to hit the GCD cap. They require 50%, compared to 100% for ele shaman, the next lowest, and 200% for fire mages.
Haste is a very poor stat for arcane, as it doesn’t increase Damage per mana (DPM). Ontop of that because they can reach GCD cap with Bloodlust + icy veins, it means they can’t use haste to force more spells into there trinkets + Arcane power. Even with this change though i’m pretty sure haste stays as the worst stat for arcane, and Fire is still way better in Sunwell.
When blizzard introduced spell haste gear in Sunwell, i don’t believe they intended it to be a dead stat for aracne, which is why i think they fixed it in the next major patch. I personally think that fix was aimed more at Arcane mages, than Rogues/Ferals, but nobody really knows.
Personally i think the game would be better off leaving this in. None of these specs are very strong at the points this effects them, and it solves some issues with there classes that blizzard itself fixed shortly after creating the problems. It just so happens that we’re playing in 2.4.3 where these problems existed.
As far as i’m aware no other classes are going to be significantly effected by this change in raids.
In pvp where rogues are strong, having them be more bursty in bloodlust might be an issue, but i know very little about pvp. I’m not even sure if Rogues play with Shamans in PVP.