I struggled a bit with the shooting at first but now I'm really really feeling it. I think my early struggles were mostly due to the low health you start off with and the Dead Eye limitations. Now that I've leveled up both it's feeling real nice.
Was just terminator walking through a town absolutely destroying fools during a mission. Took some adjusting coming from RDR, which I was actively playing before RDR2 dropped, and I think I enjoy the combat in RDR2 it more. Love how tapping RT will quick draw and shoot the guy in front of you. The added gore is also a huge plus.
Dead eye is pretty OP once you begin unlock some of the advanced stuff and manage it with tonics lol, it's a great bailout but I hate having to rely on it. I still think the way the aiming feels on the sticks do not feel tight enough, and are kind of wonky. But I like how there's a timing to your shots since you have to cock your gun and the circle around the reticle is a pretty good que on when you're good to fire. Constantly mashing the trigger results in a pretty huge accuracy and damage penalty it seems. Pretty cool imo. They also took a card from RE4 with how you move while trying to steady your shot, but they took it to the next level with the wobble penalty you get while trying to walk and shoot at once. The reward for landing those shots? Looking like a badass cowboy. Still think they should've went the Max Payne route with the aiming all together (I still don't have a setting that I really like... to add to the MP3 comment: it was also able to nail physics, animation, and responsiveness in a great way). Even with the deadzone slider all the way down I still feel like there is some deadzone and that the stick isn't matching well with my movement.
Either way, I think the gunplay gets better when you find the guns you like. Cattlemans Revolver is trash, Double Action for life. The Springfield and Bolt Action rifles feel amazing.
Side Note: Duel revolver loadout + dead eye + unleashing all your clips = heaven.
EDIT: Extra Side Note: To those that are struggling in gunfights, makes sure to get the timing of you gun and shots down. They all vary. Also, make sure you are using the right guns close range, mid range, and long range.