Str does affect damage output but seriously 25 str would be bad damage
Basic stat build....
Str as amount damage should be around 80 - 99 base str, try to get multiple of 10 on total str.
For an assassin, 99 agi is overkill, 80 is good enough, you can go less or up a bit, depend on how many flee you need to hunt specific monster.
Vit kinda meh on PvM but 20 is good amount (unless you are mobbing and hit them normally)
Why you need dex when you are crit-ing?
80 luk is overkill too imo, Aim for ~40 total crit (1 luk = 0.3 crit) then you are good.
It's good to have more crit but if you are sacrificing other stat, don't do it.
50 total crit would be real bish, you should not go more.