First off, some quick questions that came up during play.
1. Do peasent kills advance Khorne's track? At first we said yes but the wording says "enemy figures" while peasants seem to be referred to as "tokens" rather than "figures".
2. When Slaneesh is controlling a unit can he spend points to resummon it to another region?
3. How are the discards chosen from the "Meddling of Skaven" card? Random? The owning player chooses (kind of useless then)?
So, after a marathon session, our group doesn't see how Tzeentch can realistically hope to win (barring getting very lucky with the old world cards). Khorne has his dial advancement, Nurgle his victory points, Slaneesh gets dial advancement AND points from nobles, Tzeentch gets...warpstone which does nothing except ruin your "stronghold" regions faster. I read the older Tzeentch thread and even people who have played over 20 games have never had a Tzeentch victory, so it can't just be a simple case of "he's the toughest god to master, people just don't know how to play him yet".
The main problem is Tzeentch has one of the most difficult dial advancement conditions (based entirely on luck, warpstone hurts your efforts, the requirement of 2 means you'll always have the least number of viable dial advancement regions out of anyone) and he's the worst for scoring victory points (worst unit stats in the game, least number of warrior figures, cards don't really balance it out, Khorne has better stats, Nurgle better numbers, Slaneesh better defense).
"But what about magic symbols!" you say. "Tzeentch can put them anywhere!" The problem with that is his cards that provide magic symbols are more the most part otherwise entirely useless, and they're expensive. There's also the cost of the 2 cultists you'll need for the corruption. That's a lot of power points! "But other players can also play into his hand by playing their cards with magic symbols!" Yeah, but if other players are playing those cards, chances are they're being played in contested regions, and Tzeentch is the worst god in the game for confrontation.
Your only hope is setting up a stronghold in some ignored corner like the badlands, troll country, or Norsca. If the starting warpstone is in the contested populous regions, you're screwed. If you do that though, you're boned for victory points and you're still not going to keep pace with the others for dial advancement (you need a bare minimum of 2 advancement tokens to get two ticks, more likely 3-4. Warpstone and magic tokens just aren't going to be consistantly common enough for that to happen).
His other big problem is the complete lack of synergy between his dial advancement and victory point efforts; his is the absolute worst in that regard (even Khorne). The manual says he has a shot at either a VP or dial advancement win, but we can't possibly see how he can expect a VP win. His stats are too weak to muscle out others from high score areas, and all of his upgrades/points are dedicated to mitigating the most difficult dial advancement condition in the game, not to give himself an advantage over the other gods, but simply to try and keep parity with them. Slaneesh can prevent combat and his high defense units from dying, which helps both his VP and dial efforts. Same with Nurgle's cultist and greater demon upgrades. Khorne is so good at his dial advancement that he doesn't need much upgrade help for VP, but his greater demon upgrade is there as an option for that. Tzeentch's cultist and greater demon upgrade serve only to desperately try to keep your options open as you try to relocate and be left alone.
Then there's his chaos cards. Again he seems to draw the short straw out of all the gods. Half of them are entirely useless for anything but trying to mitigate the most difficult dial advancement in the game (dazzle, that one that stays if he kills a unit (good luck with that)). Teleport is useless against cultists (you're paying 1 point and a card slot to teleport them away when the other player can simply spend 1 point to teleport/resummon them back), plaguebearers (same deal), and not really worth the bother against demonettes. Warp shield's one utility is keeping your Lord of Change alive, but then they can still kill your cultists and you still lose. Meddling of Skaven is almost always a waste of a point. Tzeentch is supposed to be the master manipulator, and the manual even says that his strength is using tons of low cost cards to control the game flow and stall, but every other god is better in this regard. Khorne gets a much better teleport (Khorne! The most inflexible and unsubtle god!) and can freeze everyone's corruption efforts, nurgle is a much better staller, and Slaneesh gets much better manipulation/manuevering cards in addition to being a better staller (all those power points). Everyone says Khorne is the power point hungry, but I say it's Tzeentch. You have to constantly spend points to relocate warpstone, summoning your Lord of Change for the magic symbols, and keeping 2 cultists in all those areas.
So where does that leave Tzeentch? It seems like the best he can hope for is to influence who wins, but can never hope to win himself. He's the worst at both dial advancement and victory point accumulation. He has the worst chaos cards. Two of his upgrades are mandatory and even then you're just playing catch up instead of getting huge advantages like zero cost lepers or defense 2 seductresses. He's just a weak god with too difficult goals.
How to fix him? I"m not sure. He definitely needs better chaos cards (2 power points for dazzle? Seriously?). His dial advancement condition needs reworking too. Reducing it to only 1 warpstone/magic would probably be too much. Reducting it to only one corruption token in a 2 warpstone/magic region would probably be better. It would free up more power points and cultists to try and spread out and snag more corruption VPs.
If over 100 collective games have yet to see a Tzeentch victory, something is clearly wrong.