How useful is Chess.com Chess Mentor? So I've used the Chess Mentor feature on Chess.com, and completed all of the free courses, and am now using it at 1 lesson a day(extremely slow).

So, I've been considering buying a membership, namely a Diamond one. How useful is the Chess Mentor when considering non-private coaching? By that I mean a class with about 15-20 people taught by a 2000 rated player (Don't have many good players in my country). Would it give a noticeable increase in performance, or would it be just a slight improvement?
I personally don't benefit much from the mentor. However, that is just a preference in learning styles. 

However, I still highly recommend a diamond membership for the tactics trainer and videos, as a good, organized at of videos with tactics will make your rating skyrocket!

I suggest Colle-Zuckertort/London systems and Dutch stonewall.