I would guess that one's view of the utility of Fortitude is really dependant on the enviornment in which one plays. Fortitude is very versitile, having Bleed bonus (Force of Will), Untap (Freak Drive, a card which was one of the main reasons for the NRA rule), healing (Restoration, Regeneration, MotSB, Rapid Healing), but mostly it has combat defense. If you are playing in a low combat or unsophisticaed combat enviornment, then For becomes a mostly a weakish support discipline, but even then it has some really good angles.
In my group, combat is very brutal and viscious. Three or four regular players have really mean Immortal Grapple or Psyche! decks, making it very likely that S:CE/Dodge will be a bad defense. The only deck in mygroup that uses S:CE regularly is a weird Obf/Dom/Pro deck that uses Form of Mist, not for defense against a good combat deck, but to continue the Bleed when it gets blocked by non-combat decks. In this sort of combat heavy environment, Fortitude becomes very helpful, as it is very likely that it will be useful, and the other combat defenses (S:CE+Dodge) probably won't be.
In a non-combat heavy enviornment, with lots of S+B, Votes, or whatever, without everyone having 9 Immortal Grapples or 12 Psyche!'s, having alot of damage prevention is wasteful as it will gum up your hand. Using the Trap/Indomitability Fortitude combat angle becomes somewhat useless in the face of a lot of S:CE. In a non-Immortal Grapple enviornment, any deck that packs, say, 10 Majesties will be completely safe from any other form of combat, including Trap/Indomitablilty. In a non-S:CE friendly enviornment, Fortitude becomes a much more viable option as combat offense/defense.
The three basic clans with Fortitude can use it to great effect, wheither in a heavy combat enviornment or not: