As a guy who has played ALOT with Phantom i see that he performs really well against new players ( no shit sherlock) because the new players dont know the game yet and the mercs yet.
But against higher skilled players, Phantom seems quite shit. Enemies can hear you, see you ( sometimes even when you are standing or crouching still ) and the EMP also gives Phantoms away.
My suggestions are :
Make the EMP and Cloak separate abilities, but also that you can activate both of them at the same time but consume more energy.
Cloak consumes less energy and be completetly invisible while standing or crouching still.
Increase his energy pool so it can handle the EMP consuming.
Decrease cloak sounds while only using cloak mode but maybe increase it just a hinch if you are using both.
Probably not neseccary but increase Phantoms hp by 10 to maintain his combat survivability because he is quite short ranged merc with a melee potential