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

[Sen_Terrechant]

Heh, /whm for weak heals or don't play it at all? This was sadly why I played BLM and COR in FFXI.

Hey but it was PRETTY. Thats what everyone seems to want, a class that summons PRETTY primals but is useless in most serious content.