I dunno, let's break it down.
Step 1: Do damage. Goal achieved? Y.
Step 2: Take hate inevitably. Goal achieved? Y.
Step 3: Give your mages 20% longer to heal you or have TE come back up. Goal achieved? Y.
It helps you do damage faster while giving you more survivability that seems like the raw definition of a "big deal."
Put it in perspective, compare S+TE vs /NIN and utsusemi. /SAM you get to do damage but you have in any 30 second window at least 50% less survivability than /NIN, yet /SAM is the better SJ for the job in many cases because it enhances the main traits and purposes of the job itself.
The bonuses of the aftermath coupled with the increased damage output can be likened to the bonuses of /NIN -> /SAM. I'd hardly call it a "side bonus."
This is totally ignoring the fact that TE is useless against magic so it's providing a 20% extra bonus to an area where you were previously left only 25% protected (shell V)
XI Wiki


