I don't get 10th point talent ability Aspect of the Dragonhawk when I spec into it as a hunter. It's only available at level 72 from the trainer. Is this just a normal ability in this build, that has nothing to do with it's entry in the talent tree?

The talent applies to both aspect of the hawk and aspect monkey which are available at low level and aspect of the dragonhawk is combined version of both

I definitely remember being able to get Dragonhawk as soon as I spec in like with all the other 11th point powers in the talent trees. Aspect Mastery describes various bonuses for each Aspect, as well as "Aspect of the Dragonhawk - Combines the bonuses of Aspects of the Hawk and Monkey" but this is already what Aspect of the Dragonhawk does anyway when all hunters get it at 72.

There's supposed to be one you get right away that pools your Hawk and Monkey bonuses, then the devs made it available for all specs in the late game, since it was handed out to fix a contrivance in PVP anyway.

The talent tells - the bonuses that it gives to Hawk (30% + power) and Monkey (5% dmg taken) are both applied to DragonHawk (which itself is combined version of both aspects)

You remember it wrong Kiriel. It's not an ability, but a talent that enhances Aspect traits, with Dragonhawk having combined bonuses of both, since that aspect is what it is. In Wrath of the Lich King expansion you train that Aspect in the 70s levels.