Well, it's not a good idea to create tutorials and such until the very end - because they could end up changing something and then have to redo the tutorial/documentation.
Also - in regard to the combos specifically...taking advantage of them is very useful but not absolutely required. Learning about them and practising with them is a sign of mastery of the game...I don't really agree that all things should have a tutorial - something has to be left for the player to work out. I agree (partially) that a player should be informed that such a mechanism exists at all...but until release there's no telling whether that's the plan - in the human starter area there's a task which involves learning how to block correctly, maybe they'll do it that way...or maybe not. Personally, I saw it mentioned on the tooltip and experimented...though that was made easier because the character I was playing was able to create a combo field and then use it...