I am only playing a few days but did notice a few things.

First, the level of the wall decides how much defence bonus points you get.
So if you don't have a high wall means you get trampled by lacking defence.

Next is the Defence skill on both Hero and your troops.
Keep that at one and its like having a bunch of baby's swinging plastic swords around. Useless to say the best.
Its ok when you are fresh and your attacker is also but when you get higher and you fail to build defence and only go for offence you are in trouble.  Simple as that.

So balance your skills for both Hero and Troops and choose the armor type for your Hero depending on its location.
Is he/she in town? resource and defence are the main things to go for.

Moving out? Offence and defence is key there.
Kinda silly to be able to make good hits but when you are helpless in defending you die never the less.
So defence is always helpful. In and out of town. And in Town the wall gives a bonus to your defence.

Kinda straight forward.