If you're unsure what's going on, record yourself and play it back. When you do, you'll be able to point out things such as a cooldown being held for x gcds or you delaying a gcd at a certain point, screwing up with power surge, etc. In the moment, everything *feels* right, but when you look at it, you might notice a glaring mistake. That was me in A3S. I thought everything I was doing was perf and was confused how I wasn't hitting x. I recorded, rewatched, and found a segment where I just stopped attacking to handle a mechanic. Fixed that next time, suddenly my dps was where I wanted it to be.

I'll throw on my 210 gear tomorrow and hit the A5S dummy again to make sure I'm not crazy, but I know for a fact that I cleared it before getting my Sephirot weapon. So having it and failing has to be something bigger than gear.

I know this because the first thing I did when getting the Sephirot weapon was hit the A6S dummy, since that's the one I was trying to clear at the time.