As for sarcasm of the highest order, well I would expect that an instrument as expensive as this would provide something more substantial in the way of improved specs over less expensive rivals: it is not beyond the realms of expectation that players playing this instrument might want to play or practice with only headphones. Indeed why provide a headphone facility if it is next to useless? For a few dollars more Moog would do themselves a big favour and make something that does what it says.
As in include a set of Sennheiser 600 Ohm headphones perhaps? Seems to me that yes, the EPro was an expensive piece of kit (and now due to market forces the cost is even higher still by a large magnitude so this headphone issue ain't doing the resale values any harm) but if YOU don't possess the correct 'optional' equipment to make it work as the designer intended, well who is at fault?
I agree the shortcomings of such an instrument should be sorted at production stage, but as Coalport says it was a rush to get it out there before Bob died. I mean, he really was the sole driving force behind Moog theremins and I think the rest of the group figured it was his 'toy' so humour him. That's why there is so little promotion (any?) done by Moog now.