The quest is easy after you have done it once or twice, the first time is a bit nerve racking for sure. Just get a friend who has done the quest so they can block for you. I have done it at least 5 times now with 1 def 11 prayer, but never with 10hp like you are intending to do, I would recommend you bring rocktails with you to make your max hp over 10.
As a side note by the time you finish the quest you will probably get 20+ hp because you do have to attack the 4 bosses in order to retrieve the 4 diamonds.