Click down on Right Stick
Lock-On is your friend.
Also..
I hate to sound like "that guy" but...
If you're playing it as a shooter, you're playing it wrong.
I know about the lock-on and abuse it quite often. Still feels wrong. Literally, every single time I die is because of the controls. Too much stuff to keep track of at the same time. Having to move, aim and shoot all at the same time gets mighty confusing in a top down shooter.
Also, I'm not playing it as a shooter, I mostly use melee weapons, but I think the game's supposed to be played as a shooter... why else would 50% of the weapons be guns?
EDIT:
Yep, just impossible to control accurately, at least for me. I cannot for the life of me play this game and feel in control. With controller I have shitty aim, on keyboard/mouse I can't move my guy properly.
And the trial and error nature of it drives me a bit insane. If the controls were good I'd have no problem with it, but when nearly all of my deaths come about because of control issues it's hard to love.
EDIT 2:
Yeah, it gets pretty ridiculous in the later chapters that require way more precision than I can ever hope to achieve. I'm getting way too fucking frustrated.
EDIT 3:
Finished it. Worst "final boss" in the history of mankind, lol. Liked the bonus levels.