I think a large part has to do with those awful preset characters Turbine has put in. I wish they'd just convert them to what Tihocan has done with his revisited path builds. If they could explain per level, why they chose to put build points in certain places and skill points and feats...ect ect, that would help newer players a TON.
I also think that Korthos should be slightly redone to let players know about stacking bonuses and fortification. For example, maybe one of the quests can offer a light fortification belt as a reward and a hint icon can explain why fortification is important. Same thing could be done with stacking bonuses.
I had a bit of background with PnP so it was not difficult for me to understand the mechanics of the game...but learning these mechanics take a long time.