I'm planning to brew a New England IPA where I only use knocked hops and dry hopping. Is there any point in boiling for an hour? What is the minimum time I should boil for? I'm thinking maybe 15 minutes.
Certainly. The guys from Brülosophy do this with their "Short and Shoddy" series.
Make sure that you hit your OG almost before the boil, because you will not have much evaporation.
If one is doing extract brewing then it is not necessary to boil the malt at all. I have made very good beers using malt extract dissolved in hot water and dry hopping the resulting wort in the FV.
If using all grain then boiling can be useful to denature the amylase enzymes (etc) and to pasteurise the wort but that can be done in 5 minutes (or less).