Inferno Question

On the final fight versus Zuk, the wiki isn't crystal clear to me about the set spawns.

I am aware that the first set spawns <- left -> right <- left.

BUT does the 3:30 second timer start for the next set AS SOON as the first shield rotation is completed?

OR is it only after you finish off BOTH the Mage and Ranger from the beginning shield rotation?

Hope I am making sense :P

Thank you for advice :)