Can someone give me an in-depth explanation why Summoner is arguably the worst DPS?

[ViviAnimus]

Indeed, Summoner doesn't. Spell speed scales for 0.098 INT or something. The Dreadwyrm Book has SS and on top of that Summoner gets three to four imperative pieces that have spell speed on them. Summoners have perhaps 60-80 Spell speed that is absolutely useless. Considering Crit and DET scale for at least 0.25, that is worth 15-20 INT which basically translates in an equal amount of DPS.
The raw damage on Summoner is a lot lower than it is on Black Mage. Also Summoner DPS is not nearly as sustained as a BLM. A simple test on a dummy proves this. Well, multiple tests.
I did 470 in T10 with 120 weapon and ilvl 119. Now I am ilvl 126 with 130 weapon and I push nearly 500 DPS on every turn expect T11 where I simply stick at 480 for some reason. (SCH uses Eos on final phase) Also do mind that it's unmerged. So on T13 that's 480 DPS. Merged it can vary from 500 to 510 easily.
And there really is an objective way to say that Black Mage is by far the easiest class to achieve high DPS. But difficulty doesn't really matter indeed. If we dismiss difficulty, than SMN should at least be on equal footing. It does not need more utility, it needs less. Actually, just delete the Battle Raise and up their DPS, it's that simple.
The fact that there are a multitude of threads doesn't bother me and has no influence over the glaring issues with Summoner at the moment.