Does the stat build really dictate how I'll do? I've just been pouring everything into Vitality, Endurance and last priority has been strength.
It's does matter. I generally do 2 points in my weapon scaling stat, then one each in vitality and endurance. Once my stats hit around 25 I start putting my weapon scaling in another weapon scale for the weapon I use. And continue the 1 vitality and endurance. I eventually when I feel my endurance and vitality is good go back to my first weapon stat and get it to 40, no points anywhere else.
As a general rule of thumb get your weapon scaling high for damage, and keep working on that endurance and vitality. As it is important. Very important. Especially that endurance. With good endurance you can run, and most importantly combo enemies to stagger and kill them without having to run away and come back.
It's worth noting soft and hard cap in stats. Soft is about 25, hard about 40. The higher a stat the less benefit you get from a level. For example you might get 3 attack per level in strength up to 25. Then after 25 get 1 or 2 points attack per level. After 40 it might take 2 levels to get 1 attack point.
It's going to be slow coming against bosses with low weapon scaling. You really need to focus more on strength. A lot of them will one shot you anyway. You want to land the least amount of blows possible to kill them and rely more on real life skill.