Walker deserved better
Haha, I can see why you wouldn't rank them, especially Cruz. He seems to have disappeared. Probably because the actor is busy with other stuff (though he had appeared on Beyond Borders...). It was kind of dumb though because they made a huge deal about him wanting to be more involved than Strauss, but then he mostly disappeared after season 9. I get his main thing was a prop in the JJ story, but still. Plus, I hate the 200 arc so it would have been nice to have gotten a bit more of Cruz besides that arc.
And I wish the writers would have done more with Walker. I know CBS pretty much decided that there would be another character even though they had plenty of characters and weren't short. So I get it can be hard to have to work around additions like that, but I also put blame on the writers. I get Erica and the others may not have "wanted" the Walker character, but since he was there, they should have given him more to do. He came in at a bad time because it was just before the Reid arc started. This is one reason why I didn't like the second half of season 12: they did a terrible job (in my opinion) of creating a balance between the Reid arc and the cases of the week.
So yeah, I can see why you forgot Walker. I think he had potential and could have been interesting if he had been given more to do and had stuck around. But since he was only in 15 episodes and didn't have much to do, I can see why it's easy to forget him and not rank him and whatnot. I sometimes forget about Seaver being on the show since she was only in 13 episodes, though with her I feel like they did more with her character (maybe not good stuff, but they did give her stuff).