Two Sslaks or an Usslak would certainly slow the players down.
I have seen equidistant orbs work well in bringing on mage conflict, but I have also seen games where two mages have long standoffs over a zone, with neither player wanting to move first.
As you say, lots of variables are in play, but the longer a game goes, the more player interaction will be forthcoming.
Anyway, great to see some action on the Domnation front - it is an underused style of the game.