Hey, thank you for playing and giving feedback that much!
Here is my answers:

>Fighter maybe is OP
I love this topic, it makes me smile (in a good way) every time, because I often hear that Fighter is OP, or that he is the worst, or that Firestarter/Poisoner is OP, or even Vagabond. Every player explore some classes better and less others, they are not balanced too much though, but you will see changes for different parts of game, and you should unlock other skills to check (you can unlock another skill on 6th level of character, buying skillbook from skill master npc, they cost 5 crystal currency each, but unlock skills forever), later there will be quests instead of buiyng them.
Also you can unlock 2 more classes (Archer and Vandal) buy beating 3rd floor. There will be more later in development.
-Fighter is a fast mobile killer, depends on good weapon equip, you can run with shield or with two weapons.
-Firestarter is about fast damaging dots and/or burst damage (it will learn fireball skill on 6th level)
-Poisoner is more damaging prolonging dots and debuffs (it will learn toxin vial skill on 6th level, that slows your enemies)
-Vagabond is about melee/range hybrid, you choose your way of development, throwing rock can be modded to smash heads of enemies hard, or be just a spam range ability
Fighter feels better on early levels, but those other guys can impact lots of damage on higher levels and if playing more crafty and/or kiting
-Archer is obviously about archery
-Vandal is a tank, that can smash things hard as well, but slower than a Fighter, also can learn stun skill

>what is RP
CUrrently classes use three types of resources to use skills, Rage Points (RP), Trick Points (TP), and Energy Points (EP)
Rage is something like rage from WoW, you build it up, then spend it on skills
Tricks is a modified idea of energy from WoW
Energy is more like a classic mana

>relax negative value
Relax is a stat of how fast you leave combat and how faster after that you can enter relax state (if you don't move)
So decreasing it you need less time for each step (5 sec by default)
Relax state affects Energy and Rage, and has no effect on Tricks, Energy regenerates faster, and Rage decreases faster.
So, it helps to Energy users, but makes things a bit harder for Rage users, and has no effect on Tricks users.
Cloth hat armor always has innate bonus to decrease relax stat (it may change in future).

>colorblind
It is a part of trait systems to diffirentiate characters, it gives some 'pleasant' traits, some 'unpleasant', and some 'rare' cases, like this one, it will appear more rare when I will have much more 'rare' traits options, also some may find this color mode fun and interesting, hehe.

>Charge skill usage
I see how you use charge, when you touch an enemy it automatically activates autoattack, but it will be much more effective, if you would strike it manually, you will have more hit chances as hit area will be large not after your enemies, but before them, autostrike on contact was added as an option when you are too late to press it in time.

>second weapon
I see that you don't use your extraslot, fighters, vagabonds and poisoners have weapon extraslot and firestarter has crystal extraslot.
That means that your fighter can equip two weapons, or weapon and a shield, or firestarter will be able to equip 2 power crystals (those give you extra skills).
Extraslot weapons attacks have long cooldown so you won't spam two weapons just like that, but you can decrease this cooldown with some ways. So this 'fist skill' is just your second weapon, but because you have no weapons in that slot it is just a fist attack.

>getting killed
When you are on low level characters on high levels with hard difficulty you can just leave to the camp, restore your health, then go to lower levels to level up, or maybe decreasing level for first times, you will have much succes as trained and well-equipped char, than trying it over and over again as first levels. But you will have this option, when you will buy tower upgrades that let you hire more expirienced adventurers with better starter equip.

>save button
It is an interesting idea, I will think on it, thank you!

>crystal skill
For some reason you didn't get any power crystals that give extra skillsduring this vid, maybe you will get them later. Some mobs drop it at some chance.

>why slow moving mode
It should help when you need to move carefully, for example, near spikes.

>Charge skill improvements: Hits +2?
Buy default charge improved weapon attack can affect 2 targets, but with this upgrade it will attack 4 targets.
It should be named targets +2 then, but it sometimes happened that boss could get all theese hits in one go, so it is 'Hits' for now.

>32:37
I'm sorry, what was your question? Couldn't hear that.

>item equipping with drag and drop
You also can equip itemsby pressing RMB, and Shift+RMB if you need to equip something to extra slot

>crystal currency
Not sure for now how I will use it in a long run. At first they were used to improve skills, now they are for buying skillbooks from skillmaster in the Camp, and to buy power crystals from gemcutter in the Clan's Domain (you will get access there after quest line and some gold grinding)

>about stick attack speed
Cooldown of weapon attacks depends on aspd and DEX, and type of weapon. Firestarters are more focused on skill damage than weapons, so they have weapons as extra optional minor damage, but you will have more options later in development.

>steam
Going to make a steam page in this year :)

If I missed something of your questions, please, let me know.
Thank you again, and sorry if there is too much text :)