It puts a frame in the middle of your screen that intercepts all mouse clicks about 5 seconds before Searing Flame is out. This lets your clicker spam right click incredibly fast. When Searing Flame actually is cast, the frame disappears. Essentially, the "reaction time" on the part of your clicker is cut out, which is a good chunk of the overall time from the first tick to second tick.
You'll always get 1 tick. If you have a holy paladin or disc priest (and you should have at least one of these), you can use aura mastery or PW:B at every one.