I don't know how the movie will handle it...but in the comics she was a master martial artist...even knocking out Thor. She only lost to Moondragon and her father in hand to hand. Expert telepath. Also could separate her physical and astral body for a duration (kinda like Dr. Strange)
I can't spoil the movie, but in the comics, Mantis is a telepath, telekinetic, empath and clairvoyant, an extremely skilled fighter mostly due to the manipulation of pressure points, including her own, what allows her to heal herself in a way similar to Iron Fist (but more physiological than mystical).
She can use her empathy to control plants, and affect their physiology just like she does with her own body, and, through telepathy, she's capable of travelling on the astral plane.
I do know that Mantis has a degree of energy manipulation, but I'm not that familiar with it, so her MFF incarnation does seem strange to me. But it's a game.
Marvel Avengers Alliance did a better job with her, they focused on her healing powers, telekinesis, telepathy and melee skills.
I have nothing to do in Marvel Heroes 2016 anymore. I have nothing to do until the new content be implemented.
I have all heroes at lv 60, with a variety of prestige lvs and my favorites have good gear that can go through any mode. I have no reasons to farm anymore and spended around 8k of danger room merits in Cyclops T-shirts. I have 1,5k splinters to spend but nowhere to use it. I have some Gs too, but all my heroes have the costumes I like, even the ones I barely use.
Until new content appear in the game I have nothing to do or farm. Of course I still need some cosmic artifacts but then what?
Now I log only for the daily rewards...