/u/RiotMeddler are you able to share how successful Eternals were in terms of the guidelines you laid out in the post
Fairly successful. Eternals have hit the mark for a subset of players. Most players aren't interested in them, and that's fine, there's a group who are who feel good about them and have clear interest in more.
I do think they suffer somewhat from players who aren't interested in them wanting something somewhat similar (more progression avenues for example). That to me is more an issue with our baseline progression/identity offerings than Eternals themselves though.