So, this is completely random, and probably has some logistical issues that make it a non-viable solution... but just throwing this out there...
What would happen if, at random, instead of a Dolmen activating normally, it just bursts explosively. The ritualists, if still alive, are instantly killed, and all players within ranged weapon radius are thrown far out of range -- far enough that a ranged light/heavy attack would be unable to reach.
That would probably have more of an effect on the macroers just rubberbanding their gamepads or mouse buttons than it would bots (as bots seem to be able to discern coordinate points to go to), but maybe it would also make it easier to pick out the actual bots.
*shrug* I dunno. Just thinking out loud.
██████ █████████ ███████ In verity.