Amazing idea and thank you for your effort!
Here's my two cents, the changing I'm proposing will be highlighted in red.
1) CHARGE ATTACK (based on rush attack)
- cooldown = once per turn
- use costs = one attack + bonus action + movement
- effects = damage (1D4 + modifier) + chance to prone the target
I don't know how multi-attack has been implemented (haven't tried the new patch yet) but I think that a character able to perform more than one attack should be able to do more with its entire turn than any other character with just one attack. Otherwise, a tiny mage is able to match a fighter in a charge against an enemy. Another solution is to leave the cost on action+bonus action+ movement but to increase the damage based on the weapon.
2) OPENING ATTACK (based on opening attack)
- cooldown = once per turn
- use cost = 1 attack
- effects = chance to distract the target (success = next attack made with advantage)
Same reasoning as before. Since it is called "Opening Attack" I imagine should be followed by another one. A Fighter with more than one attack should be able to follow up on the first one (opening).
3.1) LACERATE (Slashing weapons)
- cooldown = once per turn
- use cost = action + bonus action
- effects = damage (weapon damage -2) + chance to inflict a stacking bleeding for 2 turn (-2HP / turn) + target has disadvantage on Constitution ST for 1 turn
3.2) CONCUSSIVE SMASH (Bludgeoning weapons)
- cooldown = once per turn
- use cost = action + bonus action
- effects = damage (weapon damage -2) + chance to block the target's bonus action and reaction for 1 turn + target has disadvantage on Wisdom ST for 1 turn
3.3) PIERCING STRIKE (Piercing weapons)
- cooldown = once per turn
- use cost = action + bonus action
- effects = damage (weapon damage -2) + chance to reduce the target's AC by 1 for 1 turn + target has disadvantage on dext ST for 1 turn
I don't have a problem with these attacks until the rogue (or characters that don't normally have multi-attack) gain proficiency in a martial weapon via a feat or by multiclassing. The corrections I suggested are only in place thinking about this situation.
Considering the amount of damage a character can dish out at higher levels, having a -2 penalty to the damage done is ok for the secondary effect of the strike, but the ability disadvantage is too powerful in my opinion.
For example, a medium tear rogue may do this trick every turn, still landing its sneak attack (which constitutes 90% of what they should do during a turn) and applying a severe debuff to the enemy saving throws without having any feat or spell. Especially the disadvantage on WIS saving throw may prove game-breaking. Said Rogue can land its sneak attack, reduce the target AC by one (which is good but not OP) and greatly increase the chance for the wizard to successfully cast "Hold Monster" or some equivalent spell that can effectively exclude the opponent for the encounter.
As said before, it is true though that the rogue has to gain proficiency in a martial weapon via feat or by multiclassing, but once that's done, you have a murdering machine on your hands.
I will edit my post later for the remaining attack but, I will say this:
In general, I would limit all these actions to
once-per-encounter. It is true that their costs are high but still, their effects are comparable to the ones of combat manoeuvres, spells or other resource-based abilities. Making them so "spammable" will consequently make all said manoeuvres, spells and abilities weaker in comparison.
