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

[Viridiana]

Its not even close to the same. Dead DPS do no DPS. Go ask any healer if there is a healing difference between DRG pre-buff and healing a SMN now. Plenty of SMN have cleared T13 with level appropriate gear.

The only difference is that DRG was a burden to heal. In level-appropriate gear, they would be clearing FCoB without the buffs they got. Were the buffs necessary despite what I just said? Yes. That doesn't mean that they weren't in the same situation SMN is in now.

And as posted earlier SMN will be fixed.
/end thread?

And yet the other classes got fixed quickly. Heck, DRG barely had time to get a reputation as being bad in FCoB before they got fixed. SMN, meanwhile, is languishing patch after patch. . .