Santa's increase to gold key chance at the end of a run makes him incredibly valuable in Heroes vs Hordes.
The base gold key chance is around 20% late game. Santa's three percentage point increase from 20% to 23% equals a 15% net increase in chance. As farming keys is the single best way to increase your power level over the long haul, that 3% chance can save you hundreds or thousands of runs to get to Heroic level gear.
