If you're in VATS mode, both you and the enemies should be in slow motion. If not, then there's a glitch occurring.
But, it sounds like you're just having a problem waiting for the kill cam to end so you can kill the next thing.
This is fixable. If you tap the VATS button during the kill cam, it will exit and you can continue doing things. The cancel button (B on Xbox) will also exit VATS. I often skip out of that kill cam and line up the next shot before the bullet gets there. This is because, even if no glitch is occurring, the enemies keep moving in slow motion while you sit there and do nothing watching your bullet.
To minimize the time spent out of VATS, tap the button to exit, then immediately hold the button to re-enter it. If you keep tapping the button, you're liable to enter and immediately re-exit, which can be bad news. Remember that you have 90% damage reduction while in VATS.
One specific time I do this on every playthrough is when fighting Kellog. I line up a crit with the fat man from the armory, fire it, and then cancel out and set up VATS shots on the synths before the mini-nuke hits Kellog.