Trying to stick to a simple combat system with some strategy.

For my game the player will controll one of nine typical fantasy heroes.

Each hero has different base stats, different abilities, and a unique set of items. Their items are stored at their home, they can carry three items. They have these items from the start. A few powerfull magical items can be obtained through the game that can be used by all, but they are very difficult to get.

I plan to have the attack stats of heroes depend completely on their weapon to not get it too complicated.

For combat I am considering to first have the player roll a D20 to see if the attack hits, and then roll a D6 for damage.
(The D20 is also used to determine what event happens when entering an area from an event list, so its already in the game.)

An encountered enemy as well as the heroes themselves will have the required number needed to be hit by their opponent listed.
Items can make a hero slightly harder or easier to hit. (a shield makes it harder, a heavy crossbow easier for example.)

If an attack misses, no damage is done. But if an attack hits, a roll for damage follows. A D6 is used for this, and the weapon damage is added to this.

The knight sword could deal 4 damage for example. A 3 was rolled. So you deal 7 points of damage to the enemy.

However, the number of someone's defense rating ignores that amount of damage. So if the enemy has a defense rating of 5, you deal 2 damage.

A typical fight would end once either one of the combatants has no hitpoints left. Players dont die but are knocked out when defeated.
If players defeat the enemy, they obtain the listed reward.

I think there should be an escape mechanic too of sorts, but I'll get to that later. Overall I think this might be reasonably balanced and allows for differentation between tanky and dodgy combatants.

Regarding the effects of different weapons:

I want to keep weapons more situational, with no clear overall best weapon in a hero's arsenal.

If 4 damage is the basic damage a weapon does for example, if a weapon does more damage its hit chance would decrease and if it does less damage the hit chance increases.
A huge warhammer could deal 6 damage, but would also have a -2 modifier to your hit chance. And a short sword that deals 3 damage could have a +1 modifier to hit chance.
All fair and balanced.

Only one weapon can be used in combat at once, so you cant use two at once to increase damage.

Every single weapon will provide bonus damage to a specific enemy type only, which is where preperation comes into play. Players should try to take the weapon with them that they expect they will need the most.

A blessed sword would do +2 damage against undead for example, in addition to its standard 4 damage. Against bandits it would only do the basic 4 damage. So its always a usefull weapon, just more usefull when you are heading to the graveyard.

None of the heroes will have a counter weapon for every enemy type in the game, so they will keep their weaknesses.
Some may also have two weapons that do bonus damage to a specific type. The palladin for example could have a slow but heavy hitting holy hammer, but also a holy sword.

I am still considering between giving each hero a single weapon that does more than the +2 standard +2 bonus damage to a specific enemy to give them a specialisation of sorts, or to make this one of their abilities instead which means they'd deal that bonus damage without needing the weapon.
Or perhaps I could mix it up and decide this on a hero by hero basis? In that case the abilty based bonus could be smaller than the weapon based bonus.

Other than this, some enemies will have unique abilities listed but they dont have weapons or such come into play. Maybe the main villain, but for now I want to focus on the most common combat in the game first.
I dont want to overcomplicate the abilities.
It will be stuff like the enemy fleeing after a single fight round, stealing an item from the player if they knock them out, more of this enemy type spreading across the board when not defeated, etc.

Thats pretty much all I have so far, I'd love to hear thoughts so I can work out the kinks, there surely must be things I might still have overlooked.