This is one of the more trickier viburnums afa location is concerned to grow and I can only assume yours are struggling in a less than ideal location. This shrub prefers a rather even climate - mild winters and not too hot summers. It is generally recommended best for zone 8, can suffer winter damage in zone 7 and not suitable for zone 6. In the PNW this plant is nearly obligatory in new landscape plantings but only on the west side of the Cascades where the climate is very mild - on the east side it is toast.

Don't know what's up with the hydrangea, although IME this is a more sun tolerant form of hydrangea and will bloom better in more sun than shade.

If you want a Viburnum which will do well in dry shade try a leatherleaf viburnum. It requires no care, and will flower well in deep shade. As to the Oakleaf Hyd., I have some in full afternoon sun that bloom profusely, while the one I have in shade gets minimal blooms, even the fall color is better with more sun.