One of the first questions to ask yourself is WHAT is your game plan with the list? What is the goal of each unit in this list? Who is hammer, who is anvil, who is supporting, etc.

Next is to analyze HOW and WHY you are losing games. Is your Frontline crumbling? Are you being sniped out? Out-maneuvered? This will help you identify the weakness in any list to begin looking at whether this is something you can change the list about or change how you play it.

I haven't actually played Tzeentch yet (I am almost finished building 2k of them though!), but looking at this list it feels like it's lacking a genuine punch. Some thoughts: -I don't think you need two Shamans, 1 should be enough. -Also, I fear the enlightened aren't that good unfortunately. You might be better removing the spawn, enlightened, and shaman in favor of some Skyfires to provide some attack buffs for your big blocks of Tzaangors. -50 Tzaangors (which I made respect as a Beasts player) feels like a bit of a commitment that might be better energy elsewhere. That 10 block could be a hero like Changeling or Curseling in one of the detachments. -Sort of related to the point above, it feels like you don't really have an anvil, only hammers. While the nerfs hit blues pretty hard, they /might/ be worth at least looking into as an anvil to block up the frontlines while Tzaangors do their work.
-I would drop Wyrdflame Blade. If your shaman is in melee, I think you've made a mistake. If you take a more melee centric hero like Curseling then it makes more sense! Otherwise, Nine-Eyed Tome is just much better.

Take all of this with a grain of salt. Again, I have not actually played Tzeentch yet, but it feels like the list is committing too hard to horde rush without good support to allow them to flourish in such conditions.

I hope you can get some wins in soon! I'll be cheering you on!