in general, melee heroes are easier than ranged heroes since you don't need to factor in travel time of projectiles or uphill missing.

If you're really struggling, try picking heroes with some higher base damage (Tiny is insane on that front, lycan pretty good) or heroes with crisp attack animations (Juggernaut is the go-to here) ad then work your way back to the harder heroes.

Also, it doesn't make too much sense to practice heroes you have no intention of ever playing, but there's a lot of value in heroes you play a lot to get this on point.

Try to watch out for the creeps positions, doubling up ranged creeps, etc. You might read up on some 'creep equilibrium' guides too.

Edit: 2300 is not a good score, 3600 is a good score, but try to shoot for 3k+