PoE combat is crap. PoE maps layouts are badly randomized, not interactive and contain very few monster types. They are nevertheless moddable and include a few encounters. What I am describing is more like:
- D3 combat
- New engine allowing highly interaction with the environment
- Superb randomization of map layouts not constricted by terrain or placement of objects in it
- Superb variety of mob types, elite affixes and enemy spells/skills
- PoE map modding abilities
- Many rare and unique encounters (like in Fallout 2 for example)
For D3 atm there are not much options regarding Rifts and grinding (maybe endless Rifts if they link them somehow) since we know the game is in a maintenance mode and no core changes are coming. However, if we speak theoretically, I agree with the points you made:
- Running random maps is more fun than story/campaign/boss runs
- Constant reward is overrated by Blizzard
- Farming for level is not exciting
In terms of fun from the grinding regarding maps I'd say we need highly randomized layouts, mobs, effects and encounters, which the player could modify in specific ways to suit better to his taste. Regarding the combat I think we will all agree that D3 somehow hit the 10 with it (or is extremely close to a maximum). Combine that combat with highly diverse dungeon, rare to appear mobs, interactive battle after effects changing the environment and unique demon/merchant/crafter encounters and you have maps to be grinded for a decade.
For D3 I hope they redesign Seasons, make them 1 month long with a main stat and gems cap; improve Challenge Rifts; stop the power creep and balance the classes and skills; introduce another tier of items (primals 1.0); make Rifts, GRs and bounties equal alternatives rewards wise.