So my wife got kidnapped while I was away found this bandit infront of my house killed her the second I saw her and then I see my housecarl and then started thinking why does this guy even live here if he cant/attempt stop this kind of crap from happening?!

He was probably out drinking mead at an inn, my housecarl goes all over the place and one has never even showed up at all

If it's Heljarchen Hall, he has a lot of ground to cover, not just the house. I've not had any issues, though yes, he does cover some ground, and some have reported him as buggy. These random kidnappings are scripted, nothing to do with the housecarl stopping or not stopping it, just part of the game.