30 fps is 'good performance'?
For me, it's all about consistency (which this game does not have).
30 fps, when locked, is acceptable though I will always prefer 60 fps or higher on capable displays (though higher framerates are compromised on modern displays compared to the CRT days). Frame ordering is what is most critical.
With a 30 fps cap Second Son would feel very consistent while this 30-45 fps situation we have now feels much worse.
If this were a PC game I would probably engage a 30 fps limiter. With PC games, I find that I'm willing to sacrifice some visual quality for 60 fps but, if the sacrifices are too great, I simply drop to 30.
With Thief, for instance, I was actually having trouble holding a perfect 60 fps and I found it rather irritating. So, I simply locked it down to 30 fps and suddenly I could enjoy 4x SSAA on top of maximum settings without ever skipping a frame. Same way I played Crysis 3 and Last Light, in fact. Both could be maxed out on my system provided I limited to 30 fps.
Still, open world games last generation were notorious for dipping WELL below 30 fps regularly. Second Son delivers some of the finest visuals we've seen to date on ANY platform and manages to avoid dipping under 30 fps 99% of the time. With a framerate limiter, the game would basically operate at a locked 30 fps and feel quite consistent as a result. Thanks to the high quality post process work it would still feel great in motion.