Maybe the phaser can detect its user's eye movement and can autorotate its emitter to lock on to whatever target the user is looking at?
Or the user might point the gun at a group of targets, and the gun gently "buzzes" the user's hand at each potential target. The user then confirms with a keypress which target he wants to lock on to - and thereafter the beam will hit that target regardless of where the gun is pointing.
Is Data known to have missed with a hand phaser?
I believe he has, Too Short a Season
comes to mind as does Descent Part I
. In both cases the opponents had cover.
He's not a made killing machine, but his specs, his hand eye coordination, his ability to gauge distance, and his speed and strength and resilience do make him a formidable opponent. If his life depended on it, or the lives of others, he could probably kill a room full of people easily and quickly too.