I do wish the main Quest line was longer, luckily I knew it was short from reading here and have ignored it so far, other than talking to the Greybeards to get shouts and dragons.
There are a ton of armor sets in the game, and with enchanting you can hit the armor cap with almost any set you wish, so you are not locked into the top couple. (I personally like the Ebony)
Don't think of it as wasting anything when doing quests while maxed at 81

Have fun with it, or if you need the leveling aspect start a new character.
I disagree with you on the multiplayer aspect, I would hate to see the game revolve around "so-called balance" as other games have done. True it would not start that way but patch after patch would go to nerfing and buffing characters should they add an arena type area.