I can answer all of your points with "git gud" but ill go one by one
1) When your character get's hit, he's imobilized, until the attack of the enemy ends, resulting in your death. You can't move, roll or recover, something that the enemies don't have to worry.
invest points into poise. unlike DS1, poise no longer makes you an unflinchable tank, but it works towards your chance of being interrupted mid animation.
being hit with a dagger while in full havels will still make you flinch, but with high enough poise, that attack with the really long animations will go uninterrupted even if you are being hit.
2) The estus recover animation, takes over 3 seconds, something that makes it useless in boss fights, since a boss in 3 seconds, can do like 4 attacks at least.
ADP affects estus drinking speed, IIRC.
3) You have a great sword and attack an enemy and you can't reach him, but the enemy with a small sword, is capable to reach you and pummel your character to death.
thats just wonky hitboxes. also, level adp. it will make it much easier to dodge those "broken hitbox" enemy attacks, since your hitbox while rolling is not tied to your character model, but from point A-B.
4) The enemy lock future is broken. You have an enemy infront of you and push the lock button, but instead of locking on him, it locks on enemy that he is 5 rooms away from you and you can't see it, making your character turn he's back on the enemy, letting him to pummel you to death.
then be more careful. the lock on is fine. its not the game's fault if you are waggling the stick like crazy making it shift targets. Also, since the game was designed with "dark" in mind, even after they gutted the lighting, the "dark" remains as far as mechanics go. in a 'dark" area, lock on range is halved.
5) You push the square button to use estus and your character stands there, like a statue, after you have almost rip out the button, 5 seconds later, when it's too late, he goes to use estus, letting the enemy beat you to death.
then don't keep the button pressed.
6) Boss fights, no matter what level you have managed to be before the battle and what gear you've managed to aquire, in human form needs 3-2 hits to kill you and hollow 2-1 hits. Also 5 out of 7 of his attacks, they can reach you from one side of the room, to the other.
Just don't get hit, and use estus/health gems.
better strategy, level up, invest in good armor, level it a bit, get a good shield, level it, put at least 20 points into ADP so you can dodge, and make sure to be human for boss fights, or have the humanity ring that lowers the amount of max health lost per death.
7) And last, the roll/back step, is useless. Enemies back step/roll, takes them 3 meters away, when your character get's only half meter away.
again, level ADP so your hitbox is smaller when you roll, and IIRC, moves faster to your location.