Yes, it'd be nice if the rear headrests were smaller, but so far it hasn't been a big deal. Be glad you don't have a rear center headrest to contend with as well like the E90 loaner I had a couple weeks back. Worse, check out a Jeep JK hard top where you have rear headrests, spare wheel, and rear window washer motor assembly all blocking your field of view.
In practice though, I find with my E93 that everything hidden by the rear headrests is receding swiftly...