I'm currently a lvl 43 Ms. Marvel. And here's my scoop!
Ok so as everyone knows... defense is crap.. and crap is defense. Max health is the main stat you want on marvel followed by dodge. I'm currently sitting at 7900 hp with 2400 regen and 16% dodge.
As for your abilities, it's really quite bland and simple when it comes to marvel. The ones you want to max out are, Mighty Punch / Photon Punch / Haymaker / Stellar Flare
From that point onward you get to make some choices depending on your gear available. Ms Marvel is not a group mission soloer, she can solo them but it takes too long to be really viable.
You'll want 1 point wonders like Escape/Charge. The heal is debatable, I currently left it as a 1 point wonder with some of my gear upping it to 4-5. The spirit regen is nice to have a few points into so that you don't seem to blow through your spirit in an instant. Some people LOVE crashdown strike, but I feel as if the spirit/energy would just be better used on another taunt (I'm talking group setting here). You'll want your frontal block, and pref if you really plan on grouping a lot (which you should as MM) than you should get a decent amount of points in it to reduce the damage as well as the spirit cost.
TLDR - Ms Marvel is an AMAZING hero to have in a group. Her solo ability is perfect for solo missions, but she's not a hero that can solo the group missions easily by herself.
Ultimate - Marvel in my opinion has the absolute best ult in the game. Make sure to switch to your + power duration gear before using (I have a 79% doom medal + 16% from gear) It makes her ultimate last a minute, and if your group can't kill any boss but doom in under a minute no matter what affix they have, well your screwed lol.
My perfect build -
http://marvelbase.com/builds/generator/ms-marvel#2K2Mv2vGKGK2K2qvK