This is an example of a racking verge; in this case it did have a dry verge fitted. The dry verge had been blocked by leafs from an overhanging tree,
sending the water passed the verge and onto the felt and batten, rotting the battens and the felt.
Racking verges are a difficult problem; if the roof has a more extreme rack in the verge it is better to use guttering. In most cases dry verge will do.
A raking verge should be treated as a valley.