Are there any negatives to gaining levels? i.e. enemies will be stronger strictly based on what level your character is.
As of this post I'm level 34 (playing on PS4), and I have NOT noticed any overly strong correlation between enemy army size or quality level and player level ... it there is one, it's modest at best.
My biggest problem is boredom ... level progression slows to a crawl above 30, and after a while all battles seem the same, and XP rewards seem chintzy.