So first of all so you can understand it a bit more. It is indeed not our code. But the biggest issue is there is no real source code leak of the game. Meaning it is almost impossible to change core mechanics as stat scaling (well we actually found some wacky access but forget that for now).
And the issue with stat scaling is well known to us which is why as others pointed out we added titles/pets to increase your crit damage multiplier on a dex character. However, as those items are received stepwise you probably run into some walls here and there as you are not supposed to get the highest possible crit damage mulitplier with lower gear. If you think about it that makes a lot of sense as you would probably dominate any int/vit char in terms of damage if you had it from the start. That problem is even worse in stage. If you balance a character to be similar damage wise to a int/vit char at high gear myth without doing so by adjusting the dex crit damage like we did, you would end up with a ridiculously easy stage gameplay on dex.
Str scaling beyond 10.001 str is a x^2 function. Before that it is linear.
Oh and about the gear you need for stages to beat them is a little bit unfortuntate. Keep in mind that cs+15 and single max grade almost double the stats of an item.