As a mostly melee gamer, I love how basic attacks feel in this game, but the damage is lacking, and I've noticed quite a few people build hybrid so they have a willpower dump (or rage dump if caster) or do other things to avoid using the basic attack. With the ability you have announced adding to the game to reassign left click to free movement, I thought it might be a good time to think of reasons for people to keep their basic attack on the bar. Adding skill modifiers seems like the perfect solution. You don't want to add too many new skills to the game though, 16 modifiers for each weapon combination would be too much and probably take away from doing something better! Adding 16 total basic attack skill modifiers could be perfect, or even round it up to 20 skill modifiers and make 1 modifier specific to each weapon then the rest generic for all types. I have a few suggestions for modifiers you could add:

2 modifier points - When wielding a shield in your off hand your third attack becomes a shield throw that bounces between multiple enemies before returning to your hand.

2 modifier points - When dual wielding, your 3rd attack always applies ailments.

2 modifier points - When wielding a two handed weapon, Deathblows with a basic attack have a x% chance to reset your dash attack.

2 modifier points - When wielding a staff, your 3rd attack knocks back weaker enemies. (Like a mini Eclipse)

1 modifier point - resource generation is increased.

1 modifier point - damage is increased.

1 modifier point - crit chance is increased

3 modifer points - When at full rage, your basic attack consumes all rage to deal 10% more damage per 100 rage.

3 modifier points - Adds an additional attack to the combo.

3 modifier points - If your dash attack would kill an enemy, you instead dash through it, killing it and attacking the enemy behind it.

As I said, I'm loving the game and can't wait to see what more improvements you add to the game!