Yeah, that sounds about right. I mean, her being the head ambassador is justification enough to assign "The best" to her, though didn't you say that The Tankard was fairly new to The Inquisition? In which case, he would have to be pretty trusted to be given bodyguard duty of the ambassador :P But seriously, perhaps Kas was deployed to their destination to spy/keep an eye on things (political meetings are ripe targets for assassins, after all), and is accompanying them back to Skyhold. That sounds sensible to me. :D