Actually, I think Haste started to scale energy regeneration at the end of WotLK, when Armor Penetration got removed. When I write "upping", I mean buff that mechanic.
I agree that if Haste was buffed too much, we would risk capping energy, because we couldn't use it fast enough. So yes, GCD could limit this. But energy regeneration through Haste could be buffed while still not hitting that ceiling. The other solution to make Haste a better stat has been rejected many times by the devs (let our DoTs scale with Haste).
So what other options do we have to make Haste a better stat?
Besides, buffing Haste energy regen could make our spec more desirable to play. Right now, it's a spec with some downtime (and by downtime, I mean "time not used to press buttons because we are waiting for energy to regenerate"). Some of that downtime will disappear with the removal of snapshotting from procs - but buffing Haste could make a Haste build on-par with other builds. So, we would have more choice in how to gear and we wouldn't feel penalised for having Haste on our gear.
PS: Your opinion about Shred is subjective. I'm sure that some would prefer a Feral gameplay with more burst damage, more damage from our direct damage abilities and less damage from our DoTs and auto-attacks. In fact, this kind of gameplay would look and feel more like it did in WotLK, when we had Armor Penetration. I didn't like that stat, but I preferred the damage model we had back then when compared to the one we got in Cataclysm. And no, it's not because I'm "bad" at applying DoTs at the right time, overwriting them at the right time, debuffing with FF and keeping SR up (order of mention is NOT order of priority).
It's because it leads to this laid-back style of play, where we apply an ability and then wait for the effect on the target. I'd like our damage model to move more towards having that effect right away on our target.