Some of the things I would like to see
Revamped skill trees
Preferably a skill tree for each skill. But at least a lot more sub-choices for each skill. As in 10+ nodes per skill.
Expanded endgame
Not at least including a way to replay the campaign at higher difficulty levels.
In general, all endgame activities should have the same difficulty tiers as NMDs. Which doesnt mean there should be 100 tiers though, as the NMD tiers could easily be reduced to something more sensible, like 10-20 different tiers, making each tier jump feel more meaningful.
Other than campaign as endgame, focus on making the overworld into meaningful endgame. The mere change of increasing difficulty and rewards from Helltides and Tree of Whispers would help here, but Blizzard should add more reasons to explore the base game world. More rare monsters/bosses/treasure goblins/teleports/events etc. With a difficulty, and rewards, that makes them relevant. And no, not just silly timers on a map. That is not rewarding exploration.
Speaking of endgame, all rewards should have multiple sources. As in, glyph XP should not only come from NMDs, and so on. So players got options and variety. However, it is fine if each of the main reward systems have one activity that is best for them.
Revamped itemization
Add a lot more normal affixes to the game (and merge a few existing affixes too). Current affix selection is fairly bland. As a counter to the increased RNG from more affixes, reduce the affix ranges, so there is less RNG in getting low/high rolls. A low roll on an item is always useless. While getting different affixes on an item might be useful for other builds (assuming affixes are reasonably balanced obviously).
After the abundance of useless low rolled items have been removed, the droprate can also be reduced, so players dont feel like they are drowning in items. Fewer but better drops, essentially.
Remove item restrictions. All classes should be able to use all items, even if they cant use them at full efficiency.
It is an affront to the concept of A-RPGs that all classes cant use shields for example.
Make Rares useful on their own. And not merely as crafting mats for Legendaries. One method could be crafting recipes for adding extra affixes to Rare items, balancing that choice with the current ability to turn them into Legendaries.
Fundamental item design philosophy changes
Item powers should be broad. As in, not merely affecting a single skill.
Single skill effects on legendaries and uniques belong in the skill trees. Move them there! (which goes with the expanded skill trees)
Items are meant to foster new ideas for builds, by having a broad range of applications. Not by handholding the player into a single specific build per item.
Revamp the 4 attribute stats
Each class should not have a single main stat. Make all 4 equally valuable in different ways. So you might have a Strength Barb, or an Int Barb. Etc.
Add the previously announced D4 runes
As in not D2 runewords, but rather the trigger â effect system that was planned for D4. Expanded upon of course. Should be able to combine 3-4 runes. Beside the trigger and effect runes, add a Boost/Power rune, as a third option, so you can choose between fewer but stronger effects, vs. more but weaker effects.
Paragon board changes
While changes to the 4 attribute stats should already help with making paragon boards more interesting, what is needed more is; keep adding new paragon boards. Before launch, that was one of the things Blizzard claimed they were planning to do. Then nothing.
Furthermore, add more types of effects to the board nodes. This would likely go hand in hand with adding more interesting item affixes.
Also, maybe have 2 legendary nodes per board, to make them less (literally) one-sided?
Dynamic combat
Combat is quite boring. Both monsters and players should be way more dynamic to each other. It should matter a great deal which enemies you are fighting. Not just samey blobs of enemies that you mindlessly AoE down.
Each enemy family and type should offer their own challenges. Each elite affix should offer its own challenge. This of course also comes down to difficulty balancing, the game does have some of the above already, but nobody will ever notice it, since the game is too easy.
Speaking of which, nerf player AoE hard. Single target and AoE should both be viable against different combat scenarios (and no, not just at bosses). Similarly, bring monster density down in some cases, like some groups of enemies might consist of 2 strong enemies and 2 weak enemies, instead of 8 weak enemies. Again, more diversity in encounters.
Oh, and add resistances to monsters (not immunities!), likewise to make them more varied, and make multi dmg type builds more relevant.
In general, both this and the single target vs. AoE skill rebalancing, should aim to ensure that most builds want to have multiple different main attacks. Instead of just funneling everything into a single nuke skill.
The rest
Lvling has become too fast. Slow it down. It should be fairly fast to reach 80. But 81-100 could take a good while longer. Endgame does, and should, start well before lvl 100.
Most of the game has become absurdly easy. Enemies should offer more of a challenge. Not just in some remote dungeon at lvl 100. But all the way from lvl 1.
On a similar note, oneshotting is not difficulty. Scale down monster dmg, but also drastically scale down player healing. Limit access to potions etc. Danger should come from getting overwhelmed, of your health dwindling over time. Not from a single monster randomly oneshotting you from time to time.
Crafting should focus on enhancing existing items, not creating new items from scratch, or rerolling items into something else. The foundation of an A-RPG should always be the dropped items.
Use the nerfhammer swiftly and often. Letting broken things remain broken unsurprisingly only leads to a broken game.
