Could be, I love the lore but i'm hardly a wow historian
Now time in wow is something strange and for me it has always been hard to grasp the times of events, wow made this even worse, as we don't age.
I do understand the point you're making, although I'm wondering how much time there is between the events of wota and the events of the black temple.
I would imagine, in all that time, in some way, he was fighting or at least preparing the fight against them. One could say that building an army to get them defeated is actively working on their defeat.
But yea, it's a bit the way you look at it, but your first comment came over as if Illidan hasn't done anything against the Legion, while the events of wota alone speak for themselves.
Another contradiction that i found in the lore are the events that are shown in the flashback with Blackrook Hold, where the mages powers are absorbed. Ingame we see this as happening inside BrH during an attack on the Hold, but in the book this happens on the frontlines of the battle against the Legion. I guess they retconned some stuff, but it did bother me a bit.