I had the idea that the reward for the overall objective is much higher if completed in faster times to make sure everyone is trying to complete the objectives as fast as possible for the larger team reward.
they already thought of this
(forum post from a dev)
One of our many types of objectives (ET fans will recognize this) is the classic "take the (thing) from X to Y". So we did have it set up such that while you're carrying it from X to Y, you're earning XP, because you're doing a good job and helping your team. And it's a nice feeling, seeing the XP accure as your rush along towards your goal. But obviously, that lead to "hmm, I think I'll hide in a corner for awhile and let the XP rack up for awhile, and then deliver it", which was bad. And so we changed it to the much more reasonable "you get your XP when you've successfully delivered it, and the faster you did so, the more you'll earn". So people who really want the XP are encouraged to deliver the thing as quickly as possible.Say some one is playing as an operative they could camp by the hack turret location but with the objective not selected and wait until the objective reward is increased before trying to complete it.
first off, I think the xp only goes up for missions where you don't even have a claSs for it, ex. you need to hack something and your team has no operatives - you would get bonus xp for switching to operative and then xp from doing the mission. And even if someone was camping out an objective, that would mean that evey other operative would have to be camping as well, and no one else on the team decided to switch to Op and do the mission - I highly doubt all these factors would be occuring all the time in matches.