Stratified economy is really, *really* good, yes. I would say that it's the best general purpose living standard, and in combination with the +0.5 influence, it makes authoritarian one of the strongest ethics.
...However, I don't think the best response to that is to nerf stratified economy, but to buff other ethics. My personal opinion:
-> Pacifist: +5 stability and +10 admin cap is much, *much* too weak for all the restrictions and the really annoying faction.
-> Militarist: The bonuses are ok, but other than that it only gives me the weakest war doctrine in the game... Can I maybe have a little more than that for an ethics point?
-> Egalitarian: If the faction didn't freak out about robots and unemployed utopian abundance pops got at least a few positive modifiers to their yields (Intelligent? Stability?), this could be much stronger.
-> Xenophile: This could potentially be really good, but right now it's held back by the pop growth system and the federation mechanics.
...If these other ethics got a bit of a buff, I think stratified economy would feel much more balanced.