to hit, agility and speed is the most important, each agility point grants 3 spd, you can also use magic, it wont miss.
if you just started playing, the first few battles are the hardests, after passing this initial stage, the game becomes a piece of cake.
you should check if your slaves are with the lust debuff, it diminish they power and speed by a lot.
lv doesnt actually matter too much except for some bonus to defense and health, most races max stats by lv 6, unless you modify them in the lab, in this case they will max by lv 8.
humans are the easiest to hit cause they default max agi is 3, while beast/half kin wolf/cat/fox is 6 (sometime sinse I last played, but its around there) so you will find it hard to hit them with physical attacks. If you can get your slaves agi to 7-12, you will aways hit and only the strongests monster will manage to hit them.