There is absolutely no need for you to step into a melee role. You are classified as a caster. Under no circumstances should you even be putting yourself that close to any mob or boss unless you are at the melee portion of your RDM rotation. And even then, you should almost always start that once your black and white mana levels are at or close to 100. RDMs in this game excel at two things: black and white magic, and combining them. Not melee.

You are only doing yourself and (more importantly) your team a disservice by trying to "melee."