This is pretty vague, but balance is the most important issue to me. D2 has been imbalanced in so many areas for so long. Patch after patch, Blizzard could never get it right.

Item balance is a huge issue. First and foremost, I'd like to see something done about the main way items are obtained by putting an end to that Boss Farming shit. Take away Boss uber-drops altogether (first time boss kill giving a good drop). Make it so people have to run areas and kill mobs to find items, not just teleport to a boss over and over. Do away with the magic find modifier. Rares should have the potential to be the best items in the game. Since uniques and sets are pre-defined, characters are built around them. I hate hate hate the fact that every character uses the same few uniques/sets and the rest are garbage. Make the crappy uniques usable (almost all uniques are completely worthless, especially at their level requirement) and the godly uniques less godly. I guess I'm not sure how I'd like to handle uniques/sets. I hate it when items are so rare that you can't ever hope to get them but I hate that some items are so common that everyone uses them. In my ideal world, every character would use rares almost exclusively with the occasional unique/set. Ranting like a spaz, moving on.

Character/skill balance needs to be done right, too. Why the fuck did they ruin WW and make Blessed Hammer so godly? Isn't there a balance somewhere? Cant they test the characters/skills/builds enough to find the necessary damage (or whatever it takes) tweaks to put each character on equal footing?