This may be outside the current scope of the game, but looking into the future, would we see an node trees expand as the game progresses? Or would you focus more about adding more skills rather than expanding applications for previous ones?
Skill trees are definitely not set in stone, and we frequently add new nodes or change existing ones. We try to avoid the total number of nodes going over 30 where possible, so we're unlikely to add lots of new nodes to a tree that's already fairly large, unless we're reworking all or part of that tree. In 0.8.3 in particular several sentinel and necromancer skill trees are receiving full or partial reworks.