Listen, as long as VP are available through random heroics, then having VP drop in old raids is no biggie.
I have sorta come over to the side that I think VP from heroics should stop, and thereby stop it from old raids. However, this would destroy almost all reasons for running 5mans, therefore destroying the LFD system.
My solution would be to offer something other than VP, but that is just as enticing. Like a guaranteed Chaos Orb, Living Ember, plans or patterns, and other highly valuable mats. It may seem like a contradiction to give Embers and plans, since they are exclusive to raids and I'm suggesting making VP exclusive to raids again, but I think you have to have some sort of incentive for normal raiders to do 5mans and fill the LFD roles. The reward can be anything, I just threw out the idea of Orbs etc. But the main point is that Blizz knows they have to entice ppl to do 5mans and use the LFD system, else few ppl would do them and queues would be hours longer than they are atm.