If you think about it Mantis powers would be extremely OP if she honed them in any way, if she was a fighter, or could actually hold her own through physical capabilities, increased training and weapons/tools her powers can go toe to toe with others in the MCU pretty easily.
It doesn't take her long to incapacitate someone if she can get close enough to do it, sure shes best on a team that can follow up after her, but her powers have only been used on bigbad level threats.
Question, Hulks entire powers are based off rage, she'd still pretty easily be able to beat the hulk in a 1 on 1 fight wouldn't she? Pacify him, makes hulks rage go away, he turns into banner easy enough.
Thor she probably couldn't get close enough to actually use her powers to pacify him and do anything to follow up preventing him from continuing to fight.
Stark would probably be easy enough if she had any fighting skills if her abilities could go through armor, honestly any human probably would be on the avengers.