Somewhat, sure. Henry is approaching 30 and has an unreal amount of usage on him. He is also a freak of nature. The main issue is that their line resembles ours and offer zero amount of room for the RBs. The QB play has been even worse for them (despite some encouraging flashes from the rookie) and they don't have any other offensive weapons besides Hopkins. It's pretty amazing that Spears has been able to gain 4.7 YPC and chip in some solid receiving work. From what I've seen his frame and running style can easily handle feature back work.
Miller could still be a very good back in the league, he has some pretty good overall traits and he's really young. But there looks to be little doubt that teams passing on Spears because of his 'medical condition' will likely regret it.