Whoops, I forgot that they hotfixed the GCD to cap at 1 second rather than at 0.75 seconds because of TBC stuff and then never reverted it.
That being said, you shouldn’t be looking at your cast windows during Bloodlust/Heroism. You should be looking at your cast windows for the rest of the fight. Will adjusting the GCD for 15 seconds of a fight at a time make that much of a difference? You only get a few more casts of LB during the BL/Hero + EM window, assuming that you are GCD capped with just BL/Hero and getting a new cap for EM. I calculated 5 more casts with the GCD being returned to 0.75 seconds. You wouldn’t get the reduced GCD (or it wouldn’t matter if you did) for any other EM buff for the rest of any fight because you’d never get it back down to below a 1 second cast.
And this scenario was EXACTLY the reason why they hotfixed it back to 1 second. It might feel bad now, but it would feel worse if you still had to wait for server cycles to get your sub-1 second casts off - losing casts in the process.
On a side note, if any shaman is hitting that GCD scenario, they should be holding Elemental Mastery for outside the BL/Hero window since the extra haste is lost. I think we’re on agreement on that.