You can try to look down on people who prefer DPS as much as you want, but taking them out of their element and forcing them to play a role they are not the best at invites trouble. I've been on both sides of that coin enough times to know.
Offer something people want.
Supply vs. Demand.
Really that simple.
On another note, i see you claim that it is horrible game design that War + Nin can proc everything Red in abyssea. Were you also claiming it was horrible game design when War and Nin had basically the same tools and weren't getting invited because people thought Nin did bad DPS and War wasn't as good as Sam? How about when people only invited Thf for TH? Or didn't invite Blm at all? Or only used Smn + Rng for certain instanced fights? Or only invited Pld + Blm, Rdm, Whm and maybe 2 DDs for certain NMs? How about that only 6 people could do Salvage? This must have been the worst kind of game design to you since the playerbase trended towards Mnk, Mnk, Brd, Rdm, Blm, Thf with maybe some variations? Geez, I don't even want to bring up getting Assault points?! Or Neo-Dynamis... Or Limbus coin profit runs... Those dirty sky linkshells that didn't let everyone come as Summoner only to Byakko fights must have really put a clear picture of bad game design in your mind.
I call Abyssea fantastic game design because I have the choice of whether or not to invite more DDs, such as my friends, or whether I want to control the time it takes to get things done (amount of people lotting) by levelling either War or Nin and trio'ing with those 2 jobs plus a mage, and switching to other jobs like Thief + War + Mage, to get empyrean weapons.