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

[ViviAnimus]

The all jobs work in different ways has been debunked over and over again and is simply not true. It's not that in the sense that no matter how you hold a fight, look at it, BLM will outperform SMN in every turn and pretty much every fight. The only way you will outdo a BLM is when there are extremely movement heavy mechanics. In fights where SMN should reign supreme (T11 and 13), it still gets smashed to shits by BLM. On T10, where they shouldn't be too far behind, they get smashed even harder. BLM has a higher potentional in every fight. It's that simple. Overall, BLM is just so much better in every fight, in every mechanic.

For what SMN does and has to do, it should do more than SMN, at least in the ST department. 40 DPS difference is in no way or shape justified. It's based on raw DPS. When we look at other viriables such as burst, movement heavy fights and what have you, one can not help but conclude that none really favour SMN. There is no single mechanic or way of a fight that favours a SMN over a BLM and that is a problem. Although I am glad, that your terminology seems to have changed a bit from the sheer acceptance to potentional ways to close gaps. What SMN needs, all that it needs, is a harder hitting Fester, a shorter cooldown on Enkindle and more MP and the Aetherflow to scale with it).