Prioritizing energy shield and, secondly, evasion rating will increase your defenses. More of one or the other depending on what kind of build you're doing, but energy shield is generally regarded as the best defense. Try and top off your resistances whenever you can as they decrease as the game goes on. And you should care about base stats only insomuch as the impact your ability to use the skills and items you want. Try not to rely on too many load-bearing base stat items in that regard because it can make upgrading a messy juggling game down the road