Blistering Attacks gives Ragnaros an empowered auto attack every 10 seconds. The cooldown is reduced by 1 second every time Ragnaros hits any enemy with a basic ability. However, Empower Sulfuras, due to an oversight, does not reduce the cooldown of Blistering Attacks when hitting non-heroes.
It was apparently designed not to empower Basic Attacks that are affected by Empower Sulfuras.
Though it only mentions damage.