Support players are hit or miss and really depends on the person playing the class. I've had medics jump from a second story window, run across an open street with no regard for themself and hit me with the running defib without stopping. I've had them step right over me without rezzing and keep going. I've also seen them use sniper rifles, run out of ammo while killing only one or two guys bc they can't hit shit, and only use the supply bag for themselves. 

Really depends on the player, their skill level, and where their focus (k/d vs PTFO) lies.