What class are you playing. Usually, I like to take many more shield nodes than you would normally. Essentially you can't go glass cannon at all. You have to play a balancing act with defensive nodes. Yes, having defense is good, but if it takes you so long to kill a boss than you are more likely to get merc-d from mechanics.
If you have a certain class you are leveling look up hardcore lets say Hardcore Deadeye in google and get the talent tree. Sometimes they will divert completely from the norm and shift up to get all the evasion shield nodes first to get that defense before the damage. If you are 100% on and don't worry about boss mechanics you can be glass cannon, but if you are bad at the game like me you want some shield to protect you from being one shot.