There is no rule for this as stats' effect vary from player to player.
Stats in current version of the game work differently than they did back then.
Right now there are things such as basic damage and bonus damage, basic hit chance and bonus hit chance, basic talent and bonus talent.
For instance, the amount of basic damage you have will stay the same regardless of the opponent, e.g. you have 200 basic damage, each person you attack, you will have that value of 200 agaisnt them (which the enemy can reduce with their equipment or talents, but the amount is fixed otherwise).
But bonus damage however, it depends against each enemy, whether it's a monster from grotto or your PvP foe.
Let's say you have 500 bonus damage, now what happens is as follows:
you attack another player,
your strength is 200
your opponent's endurance is 150
200+150=350
Now you take your strength and divide that amount by total amount that i calculated previously (your STR / (your STR + enemy END)) 200/350 = 0,57 roughly, which is 57%
That means, against that specific opponent, you will use 57% of your bonus damage (however, if that opponent has equipment and talents that reduce bonus damage, the percentage will be used after the bonus damage has been reduced by their equipment/talents), which is 57% of 500 = 285
Against that player you will have 200 basic damage and 285 bonus damage (without their damage reducing equipment/talents)
Strength vs Endurance (your / total (your+opponents)) = percentage of damage that will be used in that fight
Dexteritiy vs Defence same thing, but with bonus hit chance
Charisma vs Charisma same thing, but with bonus talent
So,
more strength you have over your opponent's endurance, more bonus damage you will use in that fight.
More dexteritiy you have over your opponent's defence, more bonus hitchance you will use in that fight.
It goes both ways, more endurance you have, less damage your opponent will have against you.
Depending on your playstyle, you can PM me and I will help you with best strategies and what to do, what NOT to do,etc.