The satellite spacing is slightly different on the eastern arc but it's close enough to the western arc spacing to get the satellites with crummy signal levels, as your picture demonstrates. A 34 on 72 is not good.
I've managed to hit 61.5 and 72.7 with a carefully aimed western arc DPP LNB, but with pretty poor levels. The short spread from 72.7 to 77 just wasn't happening though. Maybe the WA DPH LNB feedhorns have a broader capture angle than the DPP's?
The satellite spacing is slightly different on the eastern arc but it's close enough to the western arc spacing to get the satellites with crummy signal levels, as your picture demonstrates. A 34 on 72 is not good.