If you play softcore a build based on strength it's best because you deal a higher damage.
Have to buy enhanced effect weapon, armor & charm with strength and also with dexterity if possible.
The more ee % you have on weapon, the more damage yo will make.
On hardcore i would play with 100 vita and rest of points in str/dex.
Here is more important to survive then make higher damage.
I also advice you to wait the opinion of a more experienced slasher :) Good luck and enjoy your time spent on Ladder Slasher!