Your beloved hunter ability is just collateral in a process that started with MoP: class ability pruning. You just didn't care about it until it affected you. The same way you now feel about AotC i felt about hunter's mark, eyes of the beast, dual wielding, wingclip, etc. It's a bit too late to cry about it now, when they realized that decade old classes can be butchered and nobody makes a peep about it.
If you think about it, the current incarnation of AotC is more akin to a real life cheetah. Cheetahs don't run for long distances at slightly increased speeds, they have a burst of speed for a few seconds at the beginning, then they get tired and slow down, just like the new talent.
I think you're mostly annoyed by the loss of convenience provided by a constant speed boost for instances or zones where you cannot mount on something faster. That can be offset by clever use of disengaging and post haste plus rocket boots.