No I am not saying it is mandatory. What I am stating is you should have first hand experience of what the raid is and how it is like with or without a defender. I will leave you to judge and know for yourself if you think it is mandatory or not. What I can do is recommend that you will need a defender to beat the King's fall raid and make it a whole less of a headache for you and everyone else. Do you need two? no you don't. Do you have to have a defender to beat it? no you don't, but with that in mind everyone must be high enough light lvl and know what they are doing to survive in both normal and hard. Why don't you just give it a shot and then state your opinion.