I'm not saying a Tzeentch list without pink horrors is unviable.
I'm saying that Tzeentch doesn't really have any alternatives for the role Pink Horrors fullfill as an effective battleline tarpit.
Nothing else brings the same, or even similar volume of wounds for their pointcost, even blue horrors don't come close to the same tarpit level.
The issue isn't the giving up of VP for kills in itself. That is fine, both from a fantasy as well as from a game-y perspective in certain situations. It can work as a mechanic on certain unit-types which represent something important being killed (e.g. generals, key-heroes) or which are sufficiently powerfull to count as an achievement to take down (e.g. big scary monsters, god-models, or even elite formations). It can also work as a general objective for a game (e.g. 1 VP per destroyed unit), though this last one is difficult to get right in an assymetrical game such as AoS.
However, Pink horrors don't fit those catagories, they're cannonfodder, a big part of their purpose is precisely to die. And giving away VP for your cannonfodder dying is rather counterintuitive and weird.
On pink horrors it's an extra, random, relativly marginal, illogical cost that solely exists for the sake of pushing its winrate slightly lower. And that isn't exactly great game design. It doesn't fit with the unit's fantasy, is game-y beyond believe, and doesn't even do anything to adress whatever makes the unit OP (assuming everyone even agrees it's OP and actually needs nerfing, but that's an entirely seperate discussion

)
It is a prime example of why balancing explicitly around winrate is tends to have rather silly results. It often results in weird game-y and illogical stuff like this that only has a marginal impact, usually on something completly unrelated to what actually makes the unit good.
Will it push Tzeentch his winrate down? Yeah, slightly.
Will Tzeentch survive? Definitly.
Will Pink Horrors survive? Probably.
Is it in any way fun or interesting? Not particularly, maybe for some die-hard min-maxers if you're lucky.
Does it make any semblance of sense outside of a purely winrate focused frame? Nope.