I also think that we lost MANY Martian Manhunter fans when he had to be powered down so much. IMO, they could have had HIM TRAIN KARA, not Alex.....and trained her well enough to not necessarily need him at every turn and only use him at specific times....like in "Falling"....that to me was one of the best fight scenes with him.....he could have also gone to get Kara and Mon-el in "Supergirl Lives" rather than Alex.
IMO, it has been the desire to put Alex front and center so much that has sidelined Martian Manhunter. Some have even gone to the point of saying that it is the "Alex Danvers" show rather than "Supergirl". I don't necessarily take it that far, but I can see their point.
I don't think that Hank had revealed himself when Alex first started training Kara so, it would have been logical for Alex to begin that process. And, I suppose the thinking afterwards was that J'onn had trained Alex (and I think continued to train her) and therefore, she would be capable of training Kara. Hank is the director of the DEO so, perhaps he is unable to get as free to train as Alex would have been.
Alex is my second favorite character behind Kara but, I agree that the second season seemed to be overtaken a bit by her character and story. As was Mon-El. From what I watched, it almost appeared as though they were the leads and Kara was a secondary character and her involvement was more a part of helping their stories move forward rather than the other way around. But, I think that this season has been flipped back to the way it should be - thus far.
I don't believe that MM was sidelined to make Alex front and center - I think it had more to do with cost of CGI, and as you stated, how difficult it was to make him look good in fights. Plus, I think that they're very cognitive of needing to keep Supergirl the strongest character, physically, and showing MM too much would negate that idea. From discussions I have seen, I think more people (comic book fans) have been put off and don't watch due to Superman being absent and made to be weaker than Supergirl than making MM weaker than her.
The fight scene between MM and SG in Falling was great. Not Reign vs. SG greatness
![:)](/media/com_easydiscuss/images/markitup/emoticon-smile.png)
but, still very good.