i am just wondering how the medic will be able to heal others. i saw in a video of a guy throwing ammo just by going near them and pressing square or somthing. will this be the same with healing or will we have a more precision based system where we actually have to aim it at people to heal them.

You need to get in a certain range (pretty close) to give someone health, and ofcourse you need to aim at this person. It's a pretty obvious system for as far as I've seen.
Things like healing and giving ammo should require no skill, otherwise it would disturd the flow of the game. I'd rather toss ammo while I'm passing someone than doing a complex handling, just to give someone a bit of ammo.

Get close and press a button to buff or toss a medkit.

How I think it works is you can buff people, giving them more health. Or you can heal all their health's fully.

this seems a little too easy but i am still unaware of what challenges enemy players provide for me to even get to the player that needs heals.

you could always wait til he's dead and throw a syringe?

Why should healing/giving ammo/buffing be difficult in the first place?

Reaching the player depends on a lot of factors: Where he is, are there many enemies nearby, can I reach that place in the first place (taking different body types in account), ...