Quote Originally Posted by Atlentor View Post
I play primary a healer but last time I tried a melee-DPS (Samurai) in an extreme dungeon.
We don't have extreme dungeons. Do you mean an expert dungeon or an extreme trial?

I moved to the back of the boss but still got killed several times by invisible AOEs.
If you look at the circle on the ground around your target, you'll see a gap in the back. This 90º gap is the "rear". Don't park inside that gap, as some bosses have rear cone attacks. Be at the edge of the gap, the boundary between flank and rear. This allows you to hit positionals without having to move more than a step in either direction, and also to dodge more easily when there is a side cone or rear cone attack. In some instances, standing inside the rear gap for too long will force an enemy to perform a rear cone attack--in this case, baiting such an attack can spare the tank for a couple seconds; just dodge after triggering it.

Next issue that I can not see if there are adds coming. This is not an issue with a ranged class.
Zoom out. Also, move the enemy list near the middle of the screen. By default it's way off to the side. You should put it where you will see it without moving your eyes much. A ghosted or darkened enemy plate in the enemy list means you cannot target the enemy. These are usually just mechanic indicators. A solid plate in the enemy list is probably an enemy that needs to die.

Third I can not see if the tank is switching the target.
In a dungeon, the tank's target is generally irrelevant. If fighting trash, you should be spamming AoE skills and switching your autoattack target to whichever enemy has the most health whenever it changes. If it's an add on a boss, the tank might not target it at all, so you'll need to keep an eye on the enemy list.