Hmmm wierd, I havent had this issue at all. In fact its quite the opposite. I've gone from 36-40 solo doing, Leve, GCleve's and can usually take 3-4 mobs my level and kill them pretty steadily. I often don't have to rest much either. A few things I noticed however..

Gear matters, I swapped out almost all my gear to lvl appropriate and non dated gear and my Armor value sky rocketed. Also keeping buffs up at all times makes things so much easier. Shell, Protect, Shock Spikes, Rampart, Sentinel, Defender ect.