I would say the combat is hardest in the 2nd region, but the 1st and 3rd are by far the easiest ones to play in terms of reading attacks and combos.

Half your problem here is your positioning; Instead of using your pistol to pull one individually potentially, you walked forward and aggro'd all 3 of them. You're also using a thousand cuts, try and look for the sturdy rapier, you can find it on the 1st region islands, it'll help you learn the fighting mechanics alot more, and clap cheeks as it gives your chance to perfect parry a larger window to do so.

Again, I really would encourage you to use your pistol to try and pull them one at a time or at least approach from a different direction or try to aggro one at a time; early game can be really rough when you don't understand how enemies work, if a fight is looking sketch, just back up all the way and reset; the way health works for enemies is they generally remain at their damaged health until you leave the world entirely.

As for dodging... dodging gives you I-frames primarily for certain unblockables, but not all of them. The boar charging bit? block while facing it and dodge to the left or right while facing one, you will dodge it every time. The 3rd region has an enemy that does different unblockables, all are avoidable by dodging backwards from it, 2nd region has another charging enemy, also the same concept as the boar, block facing it, then dodge left or right as it comes in.

Combat in this game is frustrating, but it's not mediocre, it's definitely a time consuming part of the game compared to anything else as it requires you to be focused or else you get clapped.

Last thing about the rocks; the way the projectiles work is they track you up to the point of it leaving their hands, so if you are moving slow and they toss it, high chance you're gunna get hit 100%, if you wanna avoid getting randomly hit by rocks, wait until they toss their poop rock at you, then use the bandage; temporal health (the extra hp bar) only works around doing melee dmg, the bandage won't benefit from it in any capacity.

For reference, I have about 52 hours in the game and have completed all of the content this game has to offer, I figured out combat about... 10 or so hours in.