So, here's a list of five very very simple changes that Blizzard could make with very little effort that -- in my opinion -- would make the game significantly more fun and playable for the long run...
They could make them all tomorrow and it would take barely any engineering time...
1) Fix the dead legendaries by giving them an additional affix.
This one is a no-brainer. How annoying is it when you pick up a lvl63 legendary weapon, only to realize that it is cannot possibly roll anything good. Take the Azurewrath for example. No respectable barb would use this weapon, not even as an offhand. Blizzard spent all this time developing a cool weapon, but it's basically DOA. Now, what if you got an Azurewrath with a +1 affix, and that affix was a socket? That would change everything. Thousands of people would use it as an offhand and totally build around it. Same with Skysplitter and many others. If they had just one more affix, they could be godly. But as it stands now, it is a guaranteed losing roll.
2) Add more monster density to Act 1 and Act 2.
This one is also super simple and would make the game so much more lasting. Most good D3 players have spent the last four months farming Act 3, and we would love to change scenery by doing Act 1 more often. But the monster density is too low to get the XP and drops we need. The halls of the dungeons feel empty. Double the number of skeletons and the problem goes away. Super simple. Just do it.
3) Add new benefits for non-main item stats. Ones that people can get excited about.
Here's an example...
For Barbarians, make it so that Intelligence increases your max fury, magic find, and slightly reduces your skill recharge times. Make it so that Dexterity slightly increases your attack speed and slightly increases your movement speed.
Every 100 points of Dex could equal +1% Attack Speed and +1% Movement Speed.
Every 100 points of Intelligence could equal +10 Max Fury, +10 Magic Find, and -5% recharge time for skills.
That wouldn't be enough for you to stack Dex or Int as your primary goal, but it WOULD make you feel a whole lot better when your otherwise-godly sword rolls a +239 Dexterity or when your godly Litany of the Undaunted shows up as Intelligence instead of Strength.
These changes could lead to a lot more dynamic character builds, and create value for weapons and armor that are otherwise useless to a player. Unlike the others, this change would take a few days to sketch out and implement, but could be done in a week or less. It would literally make the game twice as good in one swoop.
4) Make the sorceress shut up.
Seriously. For the love of God. Make it an option menu check box or something. I literally can't play when my girlfriend is home because if she hears the enchantress she will think less of me.
5) Never allow two identical items on the AH at once...
There are more and more reports of duping, and while it's not an epidemic yet, it is the ONE thing that can totally ruin Diablo. Heck, I quit D1 and D2 when duping became a problem. So why are multiple of the exact same item on the AH at once?
It would take Blizzard literally five minutes to put in a line of code that searches the AH to see if your item already exists on it. If an item with the same name and stats is on there, you can't put it up. In theory, they should have unique item ID's for everything in their database, but regardless, this will also go a long way to combating the problem.
And while they're at it, take another five minutes to put that same line of code in your inventory and stash. If an item is placed in either -- and an identical item exists -- it deletes both. Wow. That would take literally five minutes to code. So do it. A 'false positive' is mathematically impossible, so there are no risks really.