Remember that ancients give 3 forgotten souls and are about 10% drop. So for every 100 legendaries - 90 will give 1 and 10 will give 30 - so you'll get 120 forgotten souls. So you've gotten less than you think.
But yes you're probably unlucky. I got 5 primals before I'd hit 750 paragon.
Good point. What also adds to it is the Forgotten Souls drop from rift guardians, and all the Forgotten Souls you get from goblins and caches and so on. It's really not 1 FS = 1 legendary looted, it's much less.
Also, the question is when you cleared GR70 to unlock primals, so a chunk of those legendaries are from before that. All those things combine reduce the number. You're still unlucky, but not unreasonably unlucky. That being said, there's tons of people who are higher paragon and are not wearing a single primal. It's so rare to find a usable, well-rolled primal.
@Bagstone, yeh that last part is what hits me most of the seasons. Though this may be a small exception. Got those wiz bracers that boost your shields primal. (not great, but not bad either).