Im level 12, a somewhat pure sword and board warrior.
Lvl 12 is nothing, you are a light armour/clothy (presumably) with next to no enchanted items of any real value thus no strong resistances. TES has always had a steep learning curve, and the deck initially is always stacked very much against you. Eventually you become godlike and no one can eff with you. I'm lvl 41 w/light armour, magic and stealth and still get 1 shot killed from time to time. TES is a game of "choosing your battles" not a hack and slash in the sense that you can assuredly take on hordes of enemies with ease. Skyrim is the easiest yet, in Morrowind it was a struggle to kill a Mudcrab or Rat with the rusty dagger you are given in the intro.
'Then three more come in, one of which is a caster. In two spells I die. TWO SPELLS.
Offensive Magic + Lowby health and no resists = Death, Magic users get the best of me at lvl 41, because I haven't power levelled enchanting. It keeps the game challenging, I've come up with clever uses of shouts, backstabs and enchanted daggers for magicka damage to curb the impact casters have on a fight which I can't compete in with magicka use.
I know I dont have any magic resistance or lightning resistance but COME ON. Two spells?!?
Yes, it is that easy, TES has always been this way to my recollection.
Even if I equipped my newly gotten fast healing it wouldnt do much, and this mage with his dagger BLOCKED my shield bash twice.
How low was your stamina? Also, be glad you have a "shield bash" previous TES games didn't. Shield Up = Doesn't mean your 100% protected. Bashing with the shield is best used strategically when an enemy is swinging at you, it throws them off balance and allows you a shot at their sensitive and now vulnerable exposed side.
Good job breaking your own game bethesda, Ill go play something else till you figure out you needed the Creation Kit and modders sooner to FINISH YOUR GAME.
Games not broken bro, just challenging and frustrating. Figure out how to best the AI and tactics of the NPC's too early and its too easy if anything, I'm extremely thankful in my case that I haven't made the game too easy. A game that is hard can be figured out and overcome with trial and error. I hope you come back or stick with it, TES games can be very satisfying when figured out.