I like the Enneract system and how you obtain skills in this game. Aside from hoping that we get even more skills to play around with, I'd like to offer up some feedback.
First would be that I feel that Demetra supplies far too many of the Enneracts, which makes repeated trips to her get you most of all the wanted skills anyway. I'd prefer a larger percentage of them to be drop-only. Note that I'm thinking from a timed league perspective, because in an unchanging game, you'll get all skills anyway. But half the fun would be in playing with the skills you've got available until you slowly work toward new drops. (I'm unsure how I feel about Enneract being publicly tradeable, I'd be inclined to say no)

I also feel the system of Enneracts lends it self perfectly for different variants of the same skill. For example, Bladestorm is a strong skill, and may need some nerfing. But another way to go around it is introduce different variants. The only difference would be the available set of Skill Modifiers. "Hephaäron's Bladestorm" may have the all important node to let you spin continuously by holding it, but "Abanaar's Bladestorm" may not and have a few funky nodes that make it do other fun things.
Then Abanaar's Bladestorm, which ends up being the weaker one may drop more often, while Hephaärons spin-to-win is quite a bit more rare. Instead of nerfing it too much, you can toy around with rarity of variants too. I feel it could be more exciting to have Enneracts drops remain interesting, because another variant may drop that you've been looking for that might just make your build better or enable a new one altogether. (A different set of conversions or conditions, for example)