The Herald convertible hood was a quick bodge by the factory and barely fit for purpose. The Herald was after all just an interim model designed on the very cheap and never meant to be built for more than a few years until they made something better.
As Dions picture shows, on the TR4, Triumph did it properly. The only way you will get a Herald hood to fit properly so it keeps water out is to modify the upturn on the deck and fit some positive location as per a TR. where the hood clips down to the windscreen top is no better either.
I'd say the opposite. Compared to contemporary designs the Herald/Vitesse hood frame is very modern, pretty complex elaborate and intended to be quick and easy to operate - which, by and large, it is. Part of that was the elimination of any need to go round clipping or unclipping poppers.
Of course, the flip side is that it was fairly cheaply constructed and is more than a little fussy to get set up right (and it's possible to build the cars wrong so the hood frame will never fit properly). Add in a hood that has shrunk, not fitted properly or was never the right dimensions and you get the fairly well known "fits where it touches" effect.
Done right, they fit pretty well and, given a more modern sealing arrangement around the window glass, would be more or less leak a draught free. I'd like to think I might get mine that way one day...... I can dream.....