Fairly solid composition. The only weak point that I see is the lack of anti-armor capability, namingly, only one unit of Hive Guard. Sure, the Carnies with Devourers can perform well vs. light armor, but you want them decimating infantry. I say, drop the useless Ravenors and take additional Hive Guard or Zoanthroapes. Your opponent would do well to focus weaponry at those Hive Guard, should he/she see them, and wipe them off the table and you would certainly be overwhelmed by Mech armies.
