Yes,

I started doing it for baron mount, the kara mount and the stone drake.

The mobs are so fixed in these place (/tar milhouse) that you can easily move around with just mouse broadcast, IWT and AOE garbage down.

I am doing similar for ulduar (for the fragments, else i would just split the raidid x25 at yogg for the mount.

Somethings you need to mouse broadcast for (starting the dragon fight, using portals, not aggroing everything in the nature place, the gnome fight, etc) but other than that its pretty easy.

Watching people multibox diablo makes this look easy, your eye looks for hallway corners where you can 'realign' the characters from rubber banding lag pretty naturally.

I am not sure what the use in garrisons would be, you could likely macro a 'target fishing guy, target herb guy' for iwt maybe. i am sure people are close with how much boxing is going on for mines.