I got my quest cape around level 90. It was quite difficult fighting the bosses at my level, in fact, I died fighting the balance elemental, but I eventually prevailed. The quest cape has opened up quite a few things for me - originally with 45 defence, I set a goal to get a quest cape, but it was impossible since I needed 65 for King's Ransom. So I just adapted and got 70 defence instead, something I don't regret. It also lead me to the summoning skill - one that I tried as best as I could to avoid. Now I realise that summoning is one of the most important skills that I would need in my venture for that elusive slayer cape.