The freedom of unlocking any ability for any character is a fantastic thing, I enjoy the freedom of being able to swap to any ability or picking a different build to farm or explore with.
But I have noticed that being able to stack passive skills at the cost of reserved mana take a pretty hard swing at the difficulty of pve content. Including with damage buffs. This isn't so much a concern in pvp because such builds are relatively easy to shut down with skills.
My suggestion is to limit the number of passive skills to one or two active offensive, one or two active defensive skills, auras being the exception, and add or rework the talent tree to increase the cap.
I believe this will increase the difficulty of pve slightly, while keeping the customization alive.
Thanks for reading and let me know what concerns this kind of change would bring up.

New players still working out details but I was linked this by another discord, it looked interesting and I am starting to really fall in love with the character concepts, lore, and game play that is show cased. Looking forward to development and I am hoping to be a backer soon.