As I've already stated, I toed-in my audio only domes as described above but with no tilt. It made no difference to the sound in my room but as I said, it looks cool.
As for my HT, they fire straight ahead & not tilted up. For me, this is preferable as they provide more uniform dispersion (although not perfect due to off axis characteristics) throughout multiple seating positions - some off axis.
From what I've been reading on the net since the first of the year, several people in unrelated threads have noticed that their sound was not up to their expectations with their ribbons This is a rather new phenomena to me as I hadn't come across this subject before.
I can only assume from what I've read is that most domes are probably more forgiving in placement & require less tweaking to get them right - at least that's the experience that I've had with mine...