Arcane Nexus

[Turin]

Actually it´s a public goods game, a prisoner´s dilemma usually only has 2 players. Additionally you are arguably still better off dispelling the global on your own even if your partners don´t help instead of doing nothing at all, which is not analogous to the prisoner`s dilemma.

As for arcane nexus, the only real issue is scaling, in a game with two players, the spell is not much better than a normal gem generating global.
A simply solution would be to tie the maximum amount of pearls you can get to the caster´s astral magic level. Something like (caster level*10) should be pretty well balanced.