TwoSix
Everyone's literal second-favorite poster
I mean, yes, kind of?The cynic in me says the call for a complex martial comes largely from those who would have their cake and eat it too; who want a character with all the capabilities of a full-on Fighter but which also has spells or other quasi-magical abilities baked in for those times when fighting isn't the best course of action. Think Gish, or Warlord, or Swordsage; that type of thing, only leaning a bit toward the warrior side.
I think the whole point is that the full-on Fighter, the "hit-it-till-it-falls-over" concept, can't by definition really match up with a spellcaster in terms of overall utility and power. But there's a hole, both in provided game mechanics and in fictional trope, for a warrior-type character who's predominantly strong and tough (or possibly agile and evasive) but also has a bag of preternatural and/or supernatural tricks to call on.
It is, essentially, a Fighter++ compared to most editions of D&D (4e is the one edition that really nailed the complex Fighter). 3.5 did it with the Warblade and Swordsage, but those classes are definitely upgrades compared to the mediocre 3e Fighter.
In AD&D or B/X terms, if Fighters took 2000 XP to get to level 2, the "complex Fighter" class would probably need to be about a 2800 to 3000 XP to level, and also have a smaller Hit Die and attack progression.