It's possible that cross-platform matches could require a gamepad or it could be an advanced matchmaking option. Perhaps matches would be gamepad or m+kb only, though honestly on platinum I don't think console users would mind being carried a little.
Huge resolutions and 60fps with m+kb might sound insurmountable but I honesty believe I could quick scope mouse and keyboard users into the dirt with the ridiculous aim assist on gamepad - especially with energy drain to do the aiming for me. Not all PC users can handle higher difficulties even with such advantages and in the same lobby Platinum console users would have better gear. Skill is the great leveller.
However some classes like N7 shadow or Melee based kroguard require virtually no skill and would be as good if not better with a gamepad with auto lock on biotic charge/melee. Accuracy doesn't really matter for caster classes either so I'd argue that there is no real advantage to playing adepts on PC.
Of course who wouldn't love the option of a mouse and keyboard on consoles too?
I'm not buying a gamepad for my PC just to have a worse experience playing MEA:MP thanks 
However, it's not just the aim-assist or auto-lock-on with biotics or melee (which you also get on PC, not the aim-assist but the lock-on ... unless you're locked onto a Hunter in Krogan heavy melee and it cloaks, cheating scumbags that they are)... on PC you have much faster turning circles, 100+ FPS if your machine/monitor can keep up, obscenely twitchy mouse sensitivity, re-bound keys (medi-gel to a mouse thumb-button for reload cancelling for instance) and on most games a wider field of vision (generally tweakable)... and that's before the modding community gets involved!
Yes the biggest advantages of playing on PC are felt when playing as an infil/sniper for instance - but it's not like Adepts don't use their guns and they're just are reliant on being able to consistently headshot as anyone else, especially when using something like the Paladin (ok, Raider not so much).
I've got both a PC and a PS (1, 2 and 3 - there's no Gran Turismo for the PS4 yet so...) ... personally I find shooting anything on my PS3 takes longer than it does on PC, you're only talking fractions of a second but that's like the difference between playing a game with <10ms lag or >100ms lag - it's definitely noticeable. Still, I'll take Gran Turismo (with steering wheel, pedals and a racing chair) on the PS3, in front of the big TV and home theatre system over Project Cars ... with a controller (if I bought one) ... in front of my PC monitor (hmmmmm... I could get a small-factor PC and put that in the living room and wire it up to the TV ... the steering wheel works on both PC and PS ... hmmm, no, the missus would probably kill me ...)
I suspect Vanguards would be the class it would make least difference on as you're going to spend as much time as possible right up-close and personal where just sticking the gun in the general vicinity of the enemy and pressing fire is going to hit 