Hmm. I just started a new character last weekend and played up through level 15 so far without trouble. The character was wearing no armor and using ranged spells and dealt with not one but two spriggens that he encountered at about level 11, without incident. I think my character is using The Lord sign stone that gives
so that may have helped with the spriggens.
The issue you may be having is that armor gives very little protection to physical attacks in the beginning (and no protection to magical attacks). An AR of 100, which is pretty high for low level character will only give yuu about a 10% damage reduction. You need an AR of at least 250-300 before you notice much damage reduction, and from there the level of protection goes up pretty quickly with every increase in AR. Here is a link to a http://www.uesp.net/wiki/File:SR-graph-Armor_and_Durability.pngshowing the protection armor gives based on your AR. You can see that for the first couple hundred points of AR, the protection is minor and the curve is pretty flat, but then around 250-300, the curve slopes steeply upwards and protection increases substantially.
So, as you can see, your level 4 character wearing a full suit of heavy armor is not getting a whole lot of protection. The main benefit of wearing heavy armor is increasing the skill so you can eventually get your AR above 300 where you start noticing a significant damage reduction.
The problem with wering heavy armor is that it is heavy, which makes it more difficult to dodge and keep your distance and run from enemies. I find that keeping your distance and using ranged attacks work well against tougher opponents. Also use terrain to your advantage to seperate multiple opponents into smaller numbers so you can take them on one by one.
Learn how to bash to break an opponents attack. A bash will break a ward or an enemy spell or interrupt an attack, allowing you to get in some quick hard hits.
And finally, if you are still having trouble, put all your points into health until you get to the point where you stop having trouble.
Good luck with your game.