I think it should be possible to see what later levels in a skill will give you. Currently, you are only able to see what the next level of a skill will give you when you level up, and you can only see the next level. It should be possible to check all the levels of the skills even when you don't have a skill point to spend.
This way, players can plan ahead as to which skills they will level up at what part of the game, because they have the info about cooldown times, mana cost, damage, stun duration, etc. at any of the levels.
Sorry if this has been suggested already, but I think this is something from dota that should be brought over.