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

[SomnusNemoris]

Comparing the DPS charts is a bit silly; I just see it as something fun to do. SMN's numbers depend far too much on the performance of the others in the party. If adds die slower, that's more DPS for the SMN. More Bennus, more DPS for the SMN. If someone dies, more DPS for the SMN. This is true for BLM as well, but the impact is greater on SMN given the reliance on DoTs. I feel like T11 is the only one where you could have a fair comparison between jobs.

I'm sure Rational Gaze is pretty good, but look at the data on that chart. In every turn, his BLM and BRD died once. That makes it a lot easier to reach higher numbers. My best T13 for example was because the BLM died; I've yet to come close to that on a clean run.

Comparing DPS charts in silly in what way? Black Mage numbers also depend greatly on the performance of the team. If adds die slower = more time to flare. If more benus are alive = more targets to AoE. You do realise one extra flare on two targets = from 3-5k damage, right? Is the SCH using Selene?To make the claim that it is excessively more true for SMN to perform well in the expense of others is ludicrous and simply untrue. If you would have died instead of the BLM, his numbers would also be higher, probably a lot higher since it means an extra flare on the adds for example? You also have no data as to when the BRD and BLM died and what the circumstances are.
Another argument is that yours actually works against you. So basically, you base your argument on the uncertain premisse that these players died on important times in order that the SMN DPS is increased (e.g adds die slower = more uptime on dots), yet it is still miles behind BLM DPS. In other words, SMN DPS is usually lower in perfect scenario runs whereas a BLM will not really suffer that greatly. Seems to me that this is an argument to use for a SMN buff rather than anything else.
In simple terminology:

You make the claim that Rational Gaze his numbers are a lot easier to reach because of people dying
So we can conclude out of this that in a perfect scenario, his DPS would be less
In a perfect scenario SMN falls even further behind BLM.
According to you, SMN benefits more greatly from people dying
Therefore the discrepancy is even larger at the expense of the SMN dying in BLM's favour.

I have seen plently of BLM videos where people did not die where they easily outperform Rational Gaze. So how does your comment even work?