The archetypes could use some active feats like the main classes get. For example, druid gets access to a character level based flame blade. That one would potentially make the Blightcaster an easy one if it goes down a similar route by granting a character level based Thorn Blade. Not sure what the active feats for the other archetypes should offer, but this seems like it would be relatively easy to do, and as a long time player it feels like it would make sense to offer.