I don't think you can say a single ability (bladestorm) makes warriors blademasters. Using that line of reasoning, you could make an even stronger argument that that mages are blademasters, since they have two of their abilities (invisibility, mirror image). Blademasters are also shown wearing cloth pants, beads, and sandals. That is cloth armor, not plate like a warrior wears. Finally, mages can equip 1h swords, so it's not a stretch for them to have a melee spec that can equip 2h ones.
Do I think mages and blademasters are the same? No. But following that argument, mages are a better fit than warriors are.