I get it that Fire is not the best in one category or another, but you're saying that 4 sets are better wrt endurance drain and the other 7 are worse. Every set has some sort of hole or drawback. The point is not that Fire is "better" than the other sets at whatever specific category, but that it's good enough for the great majority of content, and has problems with a few things the way most sets have problems with a few things. Even my electric armor tank can eventually get overwhelmed by big enough piles of malta, even my ice armor tank would get mashed by stuff like Rularuu mobs.
e: huh I just noticed Fire/Temperature Protection also has 20% -recharge resist, go figure