Adrenaline shot: ONE OF THE WORST EXPERIENCES

It took me two full nights to unlock recons' 'SPAWN BEACON' via Challenge: 'Make 30 kills while adrenaline injection is active'.
Adrenaline shot is so useless and is even hard to use it while being useless...
While ''activating'' it - you're unable to shoot and the animation lasts 1.5sec. Adrenaline lasts 2 seconds and in those 2 seconds you need to make a kill and sometimes it doesn't register the kill because you didn't make it in those 2 seconds. And if you waste the ''shot'', you need to wait a minute to get it refilled or better option is to redeploy/die which is faster way to repeat the process...

CHANGE the way ADRENALINE SHOT works, balance it and make it usefull. Please!