I don't mind the questions. Clarifying things is something I do pretty often. Whither I'm on the receiving end or trying to send a message.
I am not going to ask your SMN rotation and will trust you know what you are doing. But I want to bring a few more concerns to mind...
First, game is not balanced around level 50 anymore. Summoners lost a fair bit of damage when they lost an entire DoT ability that wasn't compensated until mid-60s for example. The only reason we're not too far off from ARR days is the removal of the "fluff" stat of accuracy (which adds no damage, only ensure hits) and addition of Direct Hit. So not only we have more stats, we have more of the stats.
SMN in Stormblood not only lost the ability to stack Bio II with Bio, but it also lost Raging Strikes, 20% (or was it 30%?) is not something to scoff at. Especially since we could contagion to extend our "super DoTs" which included Miasma II (and Potent Poisoning Potion if people remember this) which we also lost. So if you sync'd at 50 and still kept RS and old contagion, I doubt you'd only get around 500 DPS. Heck, our main mechanic of Dreadwyrm Trance resetting our Tri-D to reapply DoTs without spending GCDs isn't available until 60. (I say "our" because I was a SMN main for most of HW and until 4.4 hit when I changed back to tanks and SMN is my current off-spec).
This isn't only true for SMN mind you. Every job, be it DPS, tanks or healers, changed. MNK lost a vital DoT (touch of death), damage on GCDs and oGCDs because the addition of Brotherhood and crits giving Chakra. DRG changed a lot and lost Phlebotomize and Power Surge (Whichever move that powered their next Jump). Ninja, a DoT and combo changes, etc. IMHO, most jobs are unplayable under 60 now-a-days (mainly because it feels VERY restricted with all the "fun" things are so back-loaded. Warrior's IR and DRK's TBN come to mind.). Hence now that I have all my jobs at 70 I do not touch mentor, leveling, or any other content that syncs me down and I am seriously praying of a Guild Wars 2 style level sync where stats drop below someone at that level but you retain all your abilities. But I digress. My main point here is; it is very difficult to accurately place BLU in a "rank" between the DPS jobs because of lack of balance around level 50.
On last thing, when you sync your SMN to 50, are you wearing actual ilv130 gear or are you using your lv70 gear? You lose melds and the item stat "budget" was different at ilv130 vs current gear (we can have more determination than we did back then and you lose materia effects when sync'd). Just want to know if that was also taken into account.