Do paragon levels affect the difficulty of enemies?
Solution 1:
Enemies increase in difficulty only based on your main level (1-70) and then the difficulty you choose to play on (Normal - Torment 10, or Greater Rift level, or Easy - Master V on Consoles). The paragon levels you gain after hitting level 70 do not increase the power of monsters (they stay at the same difficulty as when you were level 70 without any paragon levels).
Solution 2:
There are a lot of threads to this topic in the official forums.
- Paragon Level and Group Difficulty
- Do Paragon levels affect difficulty?
- Dynamic Difficulty and Paragon 2.0
Even if none of these has a blue answer, they all say the same: Game difficulty is only determined by character level and not affected by paragon level.
Also in my opinion it would not make much sense to implement it different. Imagine you are paragon 400 and create a level 1 character: Should be game really be 400 times harder than for a paragon 1 account?