Either Taunt or SubSplit sets will beat Chansey. I've been running Taunt + WoW Chandelure for a while now and I really suggest you try that set out because in practice you will beat the most common special walls in the tier, as Florges does little damage to you as long as you run some HP investment. Very few special attackers can achieve this in the tier, with maybe Specs Keldeo coming close. Hydreigon can't reliably beat either Chansey or Florges even with significant Atk investment. For this reason Chandelure stands out to me as the most fearsome wallbreaker in the tier.