There is a few things I'd like to add that have been said on other threads breaching this topic.
The first is that the incentives for PvP advantage only the Antagonists. The better the antagonists does the more rewards they will get period. There is only one way an antagonists can get rewarded so the incentive is self evident. Raiders, however, have absolutely no incentive to engage in PvP, because and antagonist will ONLY reduce the rewards as compared to a game verses the AI, PvE. Even if the raiders win, they will, at most, only get as much as they would if they won verses the AI. Most often, however, when they win it's at great cost and was usually a slog fest between the two sides with greatly extended time and 1 or more survival periods. This means a score of 5.5 to 6.5, maybe 7. These rewards are ABYSMAL and make it so that even when you win against the antagonists you aren't rewarded for the hard work, close game, and extreme effort put forward. It's basically the Antagonist winning anyways, because it feels like a loss all the same. So there isn't anything to get excited about as a PvEer facing an antagonists, there is nothing to look forward to that you couldn't already in PvE.
The next thing I'd like to say has to do with a solution. BeerTheBrad offered a system that would benefit both PvPers and PvEers. I wish he brought it up here, but he can correct me if I got it wrong. But there would be an option to opt in to a priority system for PvP that would mean that the match making would prioritize you more for an antagonists invasion, or inversely an option to opt out of priority so the match making would be more likely to avoid you. There would have to be incentives, of course, for opting in, like greater rewards for getting an antagonists (as it stands no no raider would have any incentives). In this system those who prefer PvP would get most, if not all, the antagonists invasions while the people who don't prefer it would get less, if at all any. This would not affect the amount of games an antagonists would get nor would it divide the community, if the numbers are scarce on either side there would be some bleed over to compensate, as the system only affects the likeliness not the outright possibility.