I'm hoping for a return to the roots of sorts with Diablo IV. I like the class systems in Grim Dawn or Last Epoch where you can specialize to give increased depth by molding rough characters into specialized elite classes. That'd give you a ton of character development. For example, a Warrior class "ascending" into a Marauder, Nightblade or Guardian somewhere mid-game depending on choices in their respective quests. But Diablo IV is probably going to play it real safe given what's been revealed about classes thus far and their very much needed Solid Title™ (so safe that I think there might just be some criticism about this post-launch)
If not this, I'd like to see Clerics!
These could take a page out of D&D and let you choose a deity to align with and be granted themed powers from. I think the Diablo games desperately need more attention to higher orders where you are not the higher order yourself, like a near-deity Nephalem in Diablo III. There's so much untapped here. The Diablo deities beyond Anu and Tathamet at best are barely known among the player base which is kind of amazing given rich pantheons are already there. Ytar is the God of the Sun, Inna is the Goddess of the Sky. And a dozen more. Call upon them to aid you in battle!
So Clerics with clubs, maces, maybe staves too, the raw D&D kind to fit in with the raw Diablo IV theme, with temporary defense and offense prayers to deities. I'd like that!
Other than this, I'd really like Amazons to get to that cool and pretty unique spear (throwing and not!) + bow combo. But Amazons are hardly a very unisex class, so maybe we need Rangers then. Demon Hunters? No, I'd rather leave that to World of Warcraft. In Diablo, we are all demon hunters.
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