arrow specialized high level npcs with ebony/enchanted/poisoned bows can two shot even a well developed and built character on master difficulty if you are not careful, and casters with high ranks of spells/dragon breaths can also make a large amount of burst dmg. (melee warriors also have similar threats but lets focus on magic and arrows like OP asked).
against arrows:
-armor is the most basic and important defence, pure casters will have a problem here, as they can only get to 300 armor rating (about 35% mitigation IIRC) while light armor and heavy armor can get to the armor cap of 556ish IIRC (80% mitigation), armor cap by itself should give you a pretty hefty survivability boost on its own 4+ arrows needed to get you (poison can still hurt more tho)
-mages get a 80% mitigation armor spell but this one is very hard to put in proper use due to its cast time, cast cost, and reduced durability (its a master spell)
-shields both light armor and heavy get acess to shields, if you are speced into a shield build arrows are pretty much a non issue for you as you can move at normal speed shield raised and immune to arrows, but even if not speced for it, if you are having problems surviving or closing in on deadly archers, use a shield to block arrows.
-movement mage and light armor builds are effective at dodging and hit and runs, keep moving, zig zagging and such, and many arrows will miss you.
-effects from spells, enchants, shouts, stone powers, special powers or pots, you can use effects like invisibility, calm, fade frenzy etc to avoid all kinds of situations, including arrows.
against spells:
-resistance, harder to come by than armor, but its even more effective against spells than armor is against melee and arrows, you can enchant neck, ring, shield and boots with either specific or general magic resistance (boots only specific) or if you are a mage from alteration tree you get both resistance and absorb (30% oh each).
there are stone powers you can pick if you dont mind leveling slower (or are done leveling) that give you resistances/hp/absorb.
and ofc pots.
-wards if you are a caster and speced into restoration its worth to learn how to use wards to protect against spells and dragon breaths.
-shields, shield spec only, but sheild build allows you to run at full speed, shield raised, with 50% spell dmg mitigation multiplicative with your base resistance IIRC.
-movement, same as arrows
-effects, same as above
Level 47 Nord Warrior. You should have a good deal of health. At least 400 at a min. Along with your armor rating of 567 (cap), any higher does nothing.
You should be able to withstand being pelted with arrows. Try to use your terrain an wait around a corner. The archers will tire and come after you. When they turn the corner, hit them in the face with your hammer.
Incoming magic is about resistance. Enchant gear with magic resistance and laugh at them as you decapitate.
not on master difficulty.
» Sat Jan 19, 2013 2:28 pm 
and arrows!? I am level 47 Nord, I have Daedra Armor, 
my Smithing level is 94! I improved the armor wearing enchantments Fortify Smithing, and potion of Blacksmith Elixir! My armor is strong, still I am being killed from low life bandits, with arrows and basic magic. 
I lose health very, very fast!
my health is 290 only! I made many mistakes to level 30, and did not understand so much what I was doing! I will make my Health and Enchantment level high! ))) Thanks, again!
