Thats the point. They are very strong and you pretty much have to avoid them, which is not that difficult in most cases, but you will need some practice and plan ahead. Get speed potion and buy a lantern. Drink the potion before you enter the caves and switch speed when necesary. Try to lure the ghoul somewhere where you can slip past it without making it chase you at full speed. If it starts chasing you, switch to full speed, try to escape the map and return again.
If you want to fight them, try befriending Zacharias. He is the strongest NPC you can recruit without having to do anything else. Suong becomes the strongest NPC if you take her with you on the first meeting with Mr. White in the basement.
Again, ghouls are meant to be avoided and caves are meant to be very dangerous. But once you get really strong, they will become a good source of weapon XP, since they respawn forever without having to rest.