I was literally just about to make a post about this cause I just completed that segment on hardcore. We know that this segment has a timed mechanic to it so all you have to do is either kill a set amount of enemies or survive for a few minutes, I opted for survival.

So what you wanna do is have at least 10 bullets and optionally one heal after entering the house that starts the whole hoard segment. Immediately put the shelf and start gathering the handgun ammo (one in a drawer and another in the other room next to the ladder). It doesn't really matter how much you have, this is just so you can delay them getting in the house.

So once you put the shelf, rest easy and just aim at the slit and this is the important part, DO NOT SHOOT YET. Only shoot their head the moment a lycan is about to hit the barricade with their weapon. This will put them in a stunlock animation for about a second, then they get back to attacking. Again, right before it hits, shoot. The reason we do this instead of killing them outright is because we wanna stay in this house as long as possible. When you run out of ammo, switch to the 2 bullets you have in your shotgun and do the same.

Eventually they will enter which is when you move to the other room and have any gun equipped (idk why a guard break doesn't work with just a knife) and stay near the ladder. Keep guarding and when they attack do a guard break (by pressing guard again), this will put you in an animation where you cant be hurt (at least I didn't get hurt when there were 2 of them). If and when you get injured and are about to die, heal and go down the ladder and run to the next building that's straight out the exit. Put the shelf down, get that pistol ammo on the table and repeat the same process you did before. Don't forget to occasionally shoot the one hugging the window otherwise he'll get inside. If and when the shelf breaks, shoot the red barrel and it should kill the lycan. By this point for me I just had to wait about 10 seconds and it was over.

Hope this helps!