Default [Q] Sense -> GPE battery life decrease?

I converted by HTC One M8 from Sense to GPe a couple of months ago. I did not receive any issues going through the process (rooting, s-off, installing new RUU). As it happens, I liked Sense and had good battery life, but the phone was crashing a lot, slowing down to a snails pace a lot, and multiple resets did not help.

On GPE, when I loaded everything up the first time, the battery life had decreased dramatically. GSAM was after a few weeks reporting ~2.20 average screen-on time. A month later, fed up, I reset the phone again, and am now getting about 4.15 average screen-on time. Better - but still not great compared to most of the posts I see on this topic.

I have Lux installed (I much prefer darker screens anyway) and there's nothing seemingly outrageous in the battery stats in BetterBatteryStats, GSAM, or Android's own. I sync photos to G+ only when plugged in, I have GPS on to Battery Saving, etc.

The one thing that feels different between Sense and GPE is that the LTE indicator seems to show generally less signal than it did before. When I switched to GPE, I did not go in and flash a new radio; when I checked, it did have the GPE radio firmware (baseband?) version installed. Recently I happened to be in the UK, where my carrier there does not use LTE, so I switched to 3G-only - and this seemingly had no effect on the battery life. Usually, I am in downtown and and northside Chicago, and T-Mobile LTE reception is generally good here.

So my questions are:
1. Is that battery life within tolerance?
2. Should I be doing something with flashing a new radio? (I think not, but wanted to check)
3. Does re-flashing the RUU seem like a good idea? (not sure exactly how, but I know its out there on other threads)
4. Could the unit be faulty? (I would have to re-set it back to Sense if so... )

Thanks in advance for any expertise you guys can offer.