Read the ability carefully. It procs your passive if evolved. That means you have the best team poke in the game (better than Jayce). You hit the whole enemy team with evolved W, run away till you see your passive buff pop back up (line of sight and bushes are good for that) and then W them again. Congratulations, you have now reduced the HP of everyone on the other team by 400 (after mitigation) and they are slowed so they can't answer well.
The AoE, slow effect, 200 passive bonus, and brush check capacity are underestimated. While I would argue that Xerath has the best poke in League (3.5 second CD, best range), Evolved Spikes provided a huge complement of Damage and Utility, infact it offers some of the best all around bonus' of each of the evolutions
The biggest advantage that Mr. Zix has over Xerath, is if things go poorly... E