I used to use a shield, but now that I've got Chrysa something (that Legandary two handed sword you get by killing the top knight), I don't use them. However, I feel like I'm wasting it, since I already have my longsword up to a hundred, and I'm not gaining any skills by killing people. But I'm not good enough at spear or blunt or short sword. I am good at bow, and have the best one in game (some unique bow that I found in a tomb...)
And I do feel that I sort of wasted my time building up my medium armor skill, since I have all heavy armor on.

However, I am a bit worried because I don't quite understand if my sword will hurt Dagoth...