I have been playing for 23 years. The defib is fun and should not be changed much, but it should go on a 8 or 12s cool down. Even the best AEDs need to charge up for at least 8s.
The only "speed" issue is ttk combined with the laser beam accuracy of some setups. Plus the vehicles felt a little flimsy. I was trying to determine if "vehicle crit points" still existed (like shooting specific points, like panels or exhaust ports etc) sometimes it felt like it did. But so much chaos going in, it could have been damaged by other sources.
The support medic is very powerful and I felt like a god sprinting through a wiped squad and bringing all 4 back in seconds, but a cooldown would add a little more pacing and tactics.
Happy hunting.