The reason it's requested a lot, is because many people would enjoy a feature like this. I am aware that people would say "choose x/y sub for this job", but even still, just the option to have some sort of control over how our jobs are built would breathe so much more life into this game's combat(for me, and many others at least).

I honestly don't think people would boot you from a group for having the wrong subs... I mean look at some of these DPS that don't even do their directionals, and DPS that deal less damage than tanks... They don't get kicked. So I don't really think pickup groups would really enforce anything. A feature like this would just add a bit more strategy and depth into the game, rather than "memorize the rotation you're given".

Heavensward should have brought something along the lines of this to spice things up a bit.