As a member of guild who did clear a reasonable number of Hard Modes in 25 before nerf, a guild that died recently, I can easily say it was a major factor in burnout.
Specifically in how these bosses we're difficult. There's nothing wrong in having bosses have more HP given our increased damage from ICC talents, but the required class stacking requirments in particular on many of these encounters destroyed guilds, or the HP requirements for things like Freya/Thorim along with the necessity of having a good amount of raid damage reduction cooldowns made it a rather frustrating experience to have to deal with.
There's currently Four or Five guilds on the server currently if I am not mistaken that are capable of killing Algalon post-nerf, given all the guilds that have died how many do you reasonably expect to even be raiding ToGC in the first place? Not much of a competition really.
ToGC should only be buffed in HP to account for the increased DPS people are doing with current talents vs what they'd do with the ones they had on retail. The real challenge in this raid is to clear it with 50 attempts left anyway.