As much as I hate to admit it, I'm going to have to try reducing the difficulty.
I did the first gate at lvl 19 (custom class, mostly warrior but some resto). I barely made it through by mustering every potion of healing I could find. By the time I got out, I leveled twice. I was therefore confident of lifting the seige of Kvatch.
However, upon entering the town, the 2 guards proceed to aggro everything in sight, then die or go unconcious, and there I am surrounded by about 8 or 10 daedra and company. Talk about a piss off. I was really enamoured with this game until I reached this point.