Here's an idea that would probably make that sort of thing just about nonviable. Pretty sure it wouldn't be a heavy lift for CG, either.
Re-arrange the Arena shards by crystal payout times in as big of blocks as possible.
If you have literally hundreds, if not thousands of players, on the same shard who can only have the same payout time... I doubt you'd see as many third party groups form to rotate people through the top spots. For example, if you had a group of 20 that was intent on giving each member a chance at #1, then a single person could only stand in line to get #1 for a single time every 20 days. No other time slots would be available for that shard. Just that one. You wouldn't be able to organize a bunch of smaller subgroups into different payout time/rank rotations.
tl:dr -- drastically increase the competition for a single payout time slot by creating shards that are defined by a single crystal payout time.