There's about a 50-50 chance I would look up dolichocephalic the first time I encountered it; I would know from context that it was a description of the guy's head and thus probably not critical to understanding what I was reading. But I might look it up out of curiousity.
On the other hand, if I encounter the word again, I'll probably look it up because that means it's not just a one-off.
I think that a lot of obscure words aren't obscure because the user is being pretentious, but are obscure because the words are no longer common. In 100 years, people will likely no longer understand the fine distinctions we make between laptops, notebooks, desktops, and tablets and will just sort of vaguely regard them as some sort of computer. In the same way most people today don't know the difference between a landau, a barouche, and a fly, and just sort of vaguely regard them as some sort of carriage.