I just ran your suggested test on Chrome on an i7 4700MQ / 16GB twice (shutting down some windows before the second run), battery settings on “power saver” and got an average of 350ms mean performance. Switching to “Balanced” and “High Performance” modes got me in the 70-80 range.
This means that you’re saying someone with their 2014 high-end laptop on power saving mode is exhibiting 2012 iPhone performance… and that’s a problem for you. If your app is so complex, the performance of a Haswell i7 in power-saving mode isn’t going to cut it, then is it really the state of JavaScript performance in Android or is it the performance of Ember?
Maybe the iPhone 6S cores are as fast per core as a Haswell i7 without power-saving switched on (if so, Bravo for them). Or maybe the 6S’s chip/browser has been tuned for this benchmark. But if I’m on the road and my laptop in power saving mode is going to bog down on Discourse, I’m not going to blame Chrome, I’m not going to blame Intel, I’m going to blame your app.