While they are level 111, they have a serious weakness to crush melee attacks. They don't have too many hit points and almost no defense bonus, so you can kill them quite quickly if you are bringing the right gear with you. The higher your level, the faster you are able to kill them.  The hardest thing about Gargoyles is the fact that you need to achieve level 75 slayer in order to kill them. This takes quite a while, however, I and many other players think it is totally worth it!