Well, he never outright says he's a fighter (unlike Roy and Thog, who have stated as much), and there's several other classes that focus on martial prowess. Ultimately it's hard to prove that anyone is a fighter, since everything the fighter can do, can be duplicated with feats.
It's from an official WOTC sourcebook, therefore it's valid for discussion in this thread. Of course, Tarquin never outright says he's a warblade, eitheris Warblade a little on the obscure side?