In this case you must have more detailed graphics for world and character.
It depends. If you choose an art style, which depends heavily on details (photorealistic direction), then a diablo like camera would avoid close up views and therefor you would need less details. On the other hand, many stylized games (diablo III itself is stylized) demonstrates, that a FPS with low details works too (eg TF2). Comparing TeamFortress 2 with Path of Exile, I would say, that it needs much more work to create Path of Exile art than TF2 art.
At least it is a good idea to reduce the workload, nevertheless, you need to limit your world extremly to handle the asset creation, regardless of what camera style you choose. A good example is grimrock , which was made by 4 people, has a clear vision (dungeon master clone) and a very limited scope, still it is FP and has amazing photorealistic art.