I've started using Guthan's armor for doing barrows. I have a question on a strategy against dharok and karil mostly. If I'm getting owned by them should I just run out of their tomb? Go through another door? Are there any other alternatives?

Please tell me that you aren't actually using guthans to kill them. Slayer dart ftw. Assuming that you are darting then I suggest leaving the room at HALF HP and getting ready to tele if you spawn another brother. If you don't, heal up on the other door (CAREFULLY) and then return. I suggest drinking a p pot and just finishing them since it is not worth the risk of the guthans parts that you might lose.