Why not make homing Arrows cost 2 Energy instead of 1?
yeah, possibly. It's a difficult balance. If arrows take zero skill to shoot they stop being fun though...
The arrows I suggested don't home infinitely, only for some time, and even with that, the arrows could get a bit dicey if they started homing in the wrong enemy, but you're the developer, so, yeah.
You could have them take a short time lock on to an enemy (hovering your Crosshair over them) so you would be vulnerable while using them. This would also stop them from targeting the wrong Enemy.