Stamina Stealing is an important stat for all players. It works similar to health steal .Stam steal dosen't take the enemies stamina. It will return stamina based on a % of the damage you do.
One of the first things combat masteries should be spent on. Until you have enough Stamina to do the attack you want. It's advise to use craft-able gear early then replace with other stats once you can gain enough stamina from your damage.