Another game's world bosses would cap each individual's rewards at 15% of the damage. They were free to score over 15% but their rewards never exceeded 15%. The result from this model is that the power players would rush to 15, stop, then go again for the final hit (and fight for first). You'd have 2-3 players getting 20-25%, 7 more getting 2-4%, the rest under 2%.

Probably the reason the cap was instilled is that there's a large income discrepancy between World Boss and the other events. The other events fail to come close to the Cerb/Baal rewards (even at the 250m boss). This is the source of the imbalance, as most anyone with a full-time job will miss both bosses.