There are gronn in Grim Batol. It makes about as much sense as everything in the Twilight Highlands Zone, not much.
I guess the dwarves of the Loch and Wetlands just twiddled their thumbs while the Bastion of Twilight was being built? Because contrary to what it felt like when patch 4.0 hit, that couldn't have happened overnight.
There's no reason why the Twilight's Hammer couldn't return to Outland and enslave them some Gronn.
I still don't understand the Bastion of Twilight.... like.. is it underground, beneath the mountain? What's up with the twisty elementium spire? Why is the entrance portal at the top of the spire? Yeah it looks cool but, why?
Also fun fact, this was an official, scrapped Cata login screen.
You just lost The Game
It's literally a portal that transports you underground. It's named GrimBatolRaid after all.