The hero's journey is a set of steps in a story. "The 12 steps of the hero's journey are...
1. The Ordinary World
2. The Call of Adventure
3. Refusal of the Call
4. Meeting the Mentor
5. Crossing the First Threshold
6. Tests, Allies, Enemies
7. Approach to the Inmost Cave
8. The Ordeal
9. Reward (Seizing the Sword)
10. The Road Back
11. Resurrection
12. Return with the Elixir"
The mentor gives the hero what he needs to answer the call after refusing it. The mentor pushes the hero into accepting the call. Sometimes this is by literally giving them what they need to succeed such as Lea giving Harry the ruby in
Changes. Sometimes it's something the hero already has like grit or an object.
Justin, Eb, and Nick Christian are literally Harry's mentors. For the purposes of the hero's journey, they are, for the most part, not. Lea is also literally his mentor, but she also often fits the hero's journey role of a mentor as well.
What Eb has taught Harry could often be considered the mentor, but it wouldn't actually be Eb because the hero's journey is a structure. It's generally considered "bad" structure to have things out of order.
At some point in almost every book, Bob could probably be said to be the mentor.
In
Storm Front, the little film canister fits the hero's journey role of the mentor.
In
Fool Moon, I don't think Harry refuses the call.
The same goes for
Grave Peril unless you assume that the call to adventure is the invitation to the vampire ball. Then Harry's own experience and skill is the mentor. (A prime example of why I'm no fan of the hero's journey. It can be bent hard enough to make work for any story because it doesn't have any real meaning).
Oooh, it'd be very cool if Rashid did act as a mentor for Harry.
To your point, Rashid fits the hero's journey mentor role to a t in
Summer Knight. It's Rashid who acts to push Harry along every step of the way and gives him what he needs to finish his journey. He could also be described as a mentor in
Proven Guilty and
Cold Days.
In
Death Masks, I can't think of a refusal of the call. The loa is probably the best example of a mentor in that one.
In
Blood Rites Harry refuses the call at Raith Manor and either Thomas or Margaret gives him what he needs to move forward. I'd argue Margaret.
Lea is in
Changes for sure. Justin is more the call to adventure in Harry's flash backs than anything else. Lea would again be a mentor in the Harry vs. Justin story.
I read once that the mentor in most westerns was the main character's grit or some other character trait. Nine times out of ten, Harry doesn't refuse the call, and it's kind of hard to say that Harry starts off in the ordinary world. Almost every time Harry does refuse the call, the first four steps of the hero's journey are Mab.
My point is that the hero's journey is mostly bull and is basically useless for analyzing what Jim is going to do. It's completely useless as a means of predicting Eb's death because Eb isn't Harry's mentor as defined by the hero's journey. Eb, Justin, and Harry aren't even properly described as mentors in their relationship to their apprentices. The proper word is master. The death of the mentor isn't a step in the hero's journey. It's lazy writing for when the mentor should obviously be the one handling the story's problem because the mentor is so much more competent than the hero. It's the same reason so many hero's are orphans (because no responsible parent would let their children go on such adventures). Eb isn't very involved in Harry's adventures. We've only seen him in five books and this excerpt from a book.
Jim is a better writer than to stick to a hero's journey script like that for each installment. He might be doing it for the whole story, but I still think you'd have to stretch some or all of the steps to their breaking points to make that kind of analysis work. The hero's journey, in my opinion, is a framework for many (maybe even most or all) ancient stories and myths. Those stories are often powerful and influential. Therefore their structure will be copied and repeated for as long as we remember them or their offspring (or their causes if Jung was correct). Sometimes the coping will be on purpose, and sometimes just because they shaped us.
But they aren't necessary parts of satisfying storytelling.
A better predictor of Eb's death is Jim's repeated declarations that he wishes to torture the reader, but that's also a predictor of every character's death. I don't take Jim too seriously on these declarations because everything could be so much worse for all the characters constantly. I've seen those stories. I don't really like them, and I don't see the point. There is enough of that in real life everyday.