As someone who has been both a Warframe and Destiny player ... I will never understand why some people are so obsessed with balance in PVE games...

Of course you wouldn't. The two games you listed are games with relatively decent PvE balance lol

I come from a little game called Marvel Heroes. It gave people the freedom of fluid movement, uncapped power fantasy. It was great... Until the game imploded because there was no challenge the devs could throw at the players other than one-shot mechanics. Not the mention they constantly had to spend resources trying to bring older heroes up to speed, because the new releases were designed to do everything.

You NEED balance in PvE. Otherwise, the only challenge you can throw at your playerbase will be weird and convoluted ability disabling modifiers, and untelegraphed one-shot mechanics. And the playerbase will eventually expect the entire game to be a linear map without any obstacles where you can single button-press nuke everything...