I have found when I am qued for group flashpoints as a tank, group finder pops fairly quickly. Likewise my healer. DPS seems to have longer to wait as either of those can fill a dps role, but a dps class can't heal or tank.
So if you are either of those, hang out on fleet qued. You can try to run back to planet and quest in between, but unless you play on week day mornings, you won't even make it to the orbital shuttle before the next group pops.
I hope you don't mean that you check both tank and dps boxes on your tank and both healer and dps boxes on your heals, because that's a douchy move. Not saying you're douchy, unless you do that.