Just keep going at it, if you got the luck and patience, you will suceed. I did it at 57 agility, spending over 2 hours on it. After rebanking for the 3rd/4th time I was about to give up, but I kept going. Now I've got the Quest Cape. :
I don't believe that is true because you are leaving out HP. Many pures avoid Hp levels so they'll have more attack + strength. When people focus on Attack and Strength, they're looking at PvP builds. Most people do PvP builds because at some point they want to PK. People who go all around, or almost all equal stats, just want higher combat or the ability to weild everything.
You could always fall down and go to the dwarves to get more food. The drunk one gives lots. That is if you have enough Hp and patience to get down there and back.
Well if you're just looking to get the Ghostly Robes you only need the requirements to start the quest. Don't worry about defeating any of the 'bosses'. You will need 53+ thieving though.