The energy balls that the Staff enemies throw at you don't actually chase you infinitely - IIRC the default lifetime is something like 20 seconds, but I can see how it feels functionally infinite.
The idea behind the pistol is that it's supposed to be powerful as fuck - but logistically inconvenient to use - making the rifle and shotgun more desirable relatively. Unfortunately it seems to be something of a recurring issue with the pistol. I'm thinking of dramatically increasing the amount of charge it takes to fire a shot to balance it out a bit.