Asthings stand right now, much as I can sympathize with complaints of top players feeling that other players gang up on them; I can also sympathize with the rational-game-theory side of the equation. If I'm a 1200 player, and two of my opponents have ratings of ~1200, and the fourth player has 1450, there's an obvious incentive for me to try working with the other 1200 players to beat the high-rated player.
The math is simple: if we team up and eliminate 1450-player, I'm left with a
1/3 chance of first place (and gaining substantial rating points from finishing over two equal players and a 1450 player)
1/3 chance of second (again, still getting decent rating points due to finishing ahead of 1450-player).
1/3 chance of third place (possibly breaking even, losing to 2 equal-players might offset beating a 1450 player)
If we don't team up, and I assume the 1450 player has a 2:1 skill edge (would win 50% of the time in an alliance-free match), then my odds are
1/6 (1/3 of the 50% that 1450 player loses): first place. As above, lots of points, but far less likely.
5/18 (27%) second place, gaining few points for beating 2 low-rated players
5/18: (27%) third place, losing a few points for losing to high-rated, with offsetting win&loss against 2 equal-rated players
5/18: (27%) fourth place, losing lots of points for losing to 2 low-rated players
I suggest that the point system be modified to offset these incentives. If left unchecked, nobody will become GM-level high player; the further someone pulls ahead in ratings, the more they will be sabotaged in their games. While it might be argued, "Hey, that's the way the cookie crumbles in 4PC", I'd retort that
1) Obviously certain players are incredibly skillful, and in a blind matchup would trounce the majority of opponents.
2) If the point system is set up / enforced in a way that precludes such high-skill players from obtaining high ratings, then... well, what's the point?
What I'd suggest is an adjustment to the point system to account for skewed match-ups. Basically, the bigger the gap between best player and average of other players:
* The fewer points top-player loses for getting 3rd/4th place. The extreme of this is, if top player is sufficiently higher-rated than other 3, her rating cannot go down at all (though, naturally, a victory is still to her credit - as per usual "beating weaker players" math).
* The fewer points bottom-3 players can win by finishing ahead of top-player. The extreme of this effect would be all 3 bottom players receiving points based only on their relative finishing place (independent of top player)
The effect should be:
A) In a matchup between 3 low-rated players and 1 high-rated player, the high-rated player is still trying to win.
B) The low-rated players are most concerned with defeating the other low-rated players (e.g. defending themselves from "dangerous" high-rated player, still seeking to get points from attacking high-rated player's pieces, but not overtly focusing on high-rated player at the risk of exposing them to attack from other 2 low-rated players).
C) In a circumstance where high-rated player neverthelss feels unfairly targeted, he/she can simply resign, losing few (if any) rating points.