The easiness comes as you progress, so by the time you get some decent equipment and 4th tier skills it's pretty hard to die. Don't even mention the 5th tier; by then pretty much everyone is a walking god. I haven't really felt like I was using my skills intelligently because everything dies so fast. It's just a matter of going through the motions. I purposefully started using worse equipment just to give myself a challenge, which is a real shame for all the loving design that went into the things I'm ignoring.
A higher difficulty level could be as simple as double health + double damage. Regional scaling should be factored in as well. Say, new regions are set at 5 levels above you from the first time you enter and stay at least 3 ahead (just throwing around numbers).
It's a fun game despite it's lack of challenge. I just wish it'd continue to be as hard as balls like the
fight near the beginning even with crazy loot/abilities.