I love Gladiator, It'd be cool to see it have its own talent tree but personally I don't think it is needed. It works beautifully as it is right now and so there is no actual need for change. With that said, more could be done with it if it had it's own tree, these recent changes were clearly an effort to buff Protection tanks while still maintaining Gladiator balance, so there is a compromise situation needed between the two.
Bladestorm, Dragon Roar, Heroic Strike, Execute, Stormbolt etc etc all took a serious damage nerf in order for them to be able to buff Protection tanks.