Yeah, you can get all 9 astral constructs with a single feat, so don't take metacreativity just for that. Telepathy is fun, but the amount of enemies just plain immune to it is annoying. There are also an irritating amount of powers that work specifically to block, negate, and even harm enemies using telepathy powers on you. If you play a Telepath, or even a psion focused that way, ask the DM to adapt Unsettling Enchantment feat for telepathy. There's really no reason not to allow it, enchantment is very similar in scope to telepathy. If he does, grab Demoralize. Now, for a single PP, you can target all enemies (and not allies) in a 30 ft area with save or shaken for min/level AND -2 penalties from the feat, whether they save or not. It's not very broken, but it is quite efficient.
Personally, I think Psychometabolism is the strongest discipline, just because of Metamorphosis and the greater version thereof. And then when you add the Metamorphic Transfer feat...