Quote Originally Posted by Deceptus View Post
My anecdotal evidence proves otherwise.

In the half second (seems longer TBH) after you cast Regen if the tank aggros the mobs, they WILL go after me the healer.

Have had regen on the tank saw them charge in, and still got aggro before. There's something funky with the system (like all systems in FFXIV).
The cast of Regen generates small aggro, but the Regen ticks themselves no longer generate aggro. This applies to all abilities with Regens, such as PLD's Holy Sheltron, GNB's Aurora, WAR's Equilibrium or SMN's Phoenix.