Sanctuary, you make a lot of good and sensible points but yet you dismiss a bit too liberally some crucial things that make mages very good and at the least more than viable. I wont deny physical > elemental because I can't be certain about Ranger, but I've dabbled with rogue & warrior enough to know how strong they're and what they can't do that mages can. I also believe than a mixed damage group is WAY better than a pure physical one (and than an pure elemental, of course).
1) They can control terrain way better than physical character.
2) They have WAY more powerful AoE damage than physical, and sometimes very easy to setup too (Hello Aero ?)
3) They have elemental affinity which IS a big factor, I wonder why you're dismissing this so easily ? It makes for insane burst potential and/or utility. I dont think physical have that kind of option.
4) Synergy between physical & elemental build are powerful. Some targets are way easier to deal with in a certain way (pure physical, elemental, one specific element etc), and if you have a mixed group, you can take advantage of this.
Your target is more sensible to elemental and your warrior looks helpless ? Not really, use them skills to enable yours mages (Phoenix Dive on your Pyro, Flay skin / Medusa Head / Oily blob).
Your target has a lot of resist / magic armor and your mage feels sad ? Enable your warrior / rogue ! Haste, PoM, Firebrand, Encourage, Teleport target at the feets of your Knight, block terrain to isolate the target, slow/cripple other targets etc. You can even use Boucing Shield for a more straightforward physical support.
5) I'm not even talking about summoner here because you already said they're good. The inner versatility of the school makes it very solid in almost all case.
Again I cant be sure about Ranger because I have yet to play one despite having already more than 150 hours on that game.
