If CS is that OP, then why are there so few people using it?
I didn't say that CS is overpowered, but rather would be on a permanent (more on this after the following). Here's why the card itself is either not overpowered, or why nobody uses it:
1.) Because mono-Entropy is not a great decktype. While Chaos Seed is almost always good, packing six of these as the only reliable source of creature control in a deck is not great. Add to that the fact that there is no permanent control or protection of any sort, and you are left with a very random, very vulnerable deck.
2.) In order to warrant the use of Chaos Seed, any deck other than mono-Entropy needs to have a glaring need for creature control that can be filled
most effectively by CS. Every other form of creature control has a specific strategic use, and works as intended 100% of the time. As a deck builder, I prefer consistency over randomness, so splashing for Rewind or Gravity Force makes more sense than splashing for Chaos Seed.
Now, as for CS on a permanent... I, for one, believe that the number one thing that needs to happen before any of this even takes shape is for CS to lose the Parallel Universe effect. Every other effect caused by CS corresponds to an inexpensive creature control spell. Parallel Universe is neither creature control
nor inexpensive, as the cheapest it ever will cost is six aether. The ability to copy your opponent's largest threat (which you should target anyway) should never cost one quantum, nor should it be a reusable spell on a permanent. This is my only objection to Chaos Seed's effects.
Putting Chaos Seed's effect on Discord implies that Discord itself is not useful and therefore should change to something more useful. I completely disagree with this. If you have ever seen what Discord can do on its own to a mono or dual element deck, you would know that Discord itself is very good. The reason nobody runs Discord is twofold: the effect of Discord is less effective against rainbow decks, of which there are many, and the supporting cast to Discord is severely lacking. I mean, really... have you seen Micro Abomination?
Another reason people don't run Discord is that outside of mono-Entropy, you have the option to play other weapons. While Discord could potentially wreck many strategies if you play it earlier, most decks are far more vulnerable to Eternity and Pulverizer. This doesn't mean that Discord itself is lacking, but rather the metagame doesn't call for it.