The problem with your point is, why aren't we spamming psykers now? 7th doesn't change anything about psyker availability, and it doesn't make powers easier to cast. Even if you do throw enough dice at a power to make it as likely to go off as it is on a leadership check, you're risking Perils, and you're denying yourself all those other powers you can currently cast.
Offensive psykers now seem weaker. Defensive psykers are now stronger. Far be it from psykers dominating the game, I think it's far more likely that this brings psykers in line.