Hey guys, I am kind of new to this game and to mmos in general.
I completed the main storyline in easy mode Bard and I created a new ninja character and it's more complicated than I thought. I am okay with dps and combos but I have a huge issue since I started these lvl40+ dungeons, I always die during boss fights, sometimes more than once. I am lvl 50 right before the ultima weapon dungeon and I'm too scared to go there because there are so many bosses and I don't want to die lol.

So, how should I position during boss fights? I make sure that my tank always has aggro on him and I can dodge the orange skillshots, but it always seems that I die to the boss' random aoe, I get hit even if I'm attacking from behind and I never see it coming. Since I am the only one in my parties to die like this I am doing something wrong and I don't know what. Can I have some advice on how to avoid that damage? It would be greatly appreciated.