Originally Posted by
blaxter
For progression (or at least if you wanna kill it first week, it's a really simple fight, as easy as jikun or the first one of ToT) you should go as arcane and reforge to either haste or mastery (if you have lot of gold also change your gems obviously). As arcane you will do a lot more damage on balls (x2 or x3 times what you can accomplish as fire), so you will reduce the number of wipes because not killing balls on time.
Seriously, if you kill leishen, ra-den is quite straightforward, just be sure everyone knows the fight after start.