I think you've said it all : SMN can reach DPS amounts equivalent to other casters but it requires way too much effort compared to other classes.
As someone said only 4 got above 4000 on EXs parse while 50+ RDM and BLM were able to.

I was not top, but okay in HS, and I barely manage to defeat Exs SSS if I do it my way. I have seen Snow's guide, I know it can get a lot better. But managing to pull it off in actual fight would require hard training.
If I sum up, they're asking main summoners with 2000 hrs+ of game to train hard as if they were newbies whilst their idea was to close the gap between lowest and top DPS ? But how would a beginner with no idea of CD, oGCD and what not could ever come close to those 4000 DPS ?

This job became very punitive. I also think it's not about the potencies (it would make great SMNs go through the roof) but how the rotation flows that should change a bit.(and don't even get me started on death, loss of pet is double punishment).