I don't have an objective gauge of "dramatic" but 50 feet still seems less than dramatic to me.
How high does a dune need to be to seem dramatic to you? At 50 feet a designer would seriously be pushing the limits. As examples, I am guessing
St Enodoc's 6th to be about 20-25 feet above the fairway
Sandwich's 4th about the same, maybe a bit less high
Lahinch's Klondyke to be a bit taller than #6 at St Enodoc
Burnhams's 10th to be about 20 feet above the tee
The tallest I would know of would be Burnham's Majuba back in the day and that would probably top out around 35 feet above what would have been the old tee. I don't know how guys did it with the old equipment.
Ciao