E12 comes well before X5 (and X3, for the matter), so you shouldn't expect it have a balance control, by your logic. Plus, balance control using full analog circuit isn't nearly as easy you as think it is. The reason why it can be implemented on E17, E07K, X3 and X5 is because of the use of hardware volume control chip (in E17, E07K and X3) or digital volume control (via X5 SoC). On the other hand, E12, which is designed to be as high a performance as it can be as an analog amp in order to appeal to the purist (*implying those who put performance over feature), doesn't have the balance control is, at least to my eyes, not illogical. Just look around, how many TOTL portable amps do you know have a balance control? FiiO even strongly consider to leave out the crossfeed feature on the next E12 reversion as they have learned from the E12DIY project that it can improve the performance. So, what is 'very important functionality' is really a matter of opinion, and no one is wrong on that matter. You might think it is important because you need it, but FiiO might think it is barely used feature from the feedback of most other user.
I do agree FiiO should label it clearly about the difference between headphone-out vs. LO, and you are not wrong to rant about it. I have ranted about the EQ on iPod causing distortion too, but I don't think Apple has intentionally came out its way to deceive me about their useless EQ. I have ranted about iriver ridiculous pricing on their AK series as well, but I am not going to keep posting hate post about iriver (consider I used to be a big iriver fan a decade ago). I have plenty of IEM that don't quite live up to their price tag as well, and I will tell people what I think about them. However, I think everyone in HF (or in life) has overpaid somethings or gotten something not up to expectation. But to keep holding grudges will be a terrible way to live. So I'll say you should by all mean rant about it, but remember to move on.
