The long and short of it is everyone has a different play style (some folks are better at it than others) and some fights are a lot harder than others. Most of the time the companions A.I. is so bad that one needs to pop a few more medpacs just to survive. There shouldn't be a limit other than the cool down. Once that's up, we should be able to pop another one if needed.
Now if you're a guru and good at surviving most all tough fights, GREAT FOR YOU! BUT if you're not a seasoned player, this ultimately turns into a very frustrating task.
BIOWARE, please change this back to the way it was!