I think your point about a shift in the value of ~VIPs away from 25K miles is well made. I'd say a VIP is worth more now, though I'm not sure as to by how much.

On to the meat of your question. I'd most certainly encourage you to do the MR and get EXP. Aside from all the benefits listed in other threads on this topic, 8 VIPs are not to be sneezed at.

As for priority, I think you'll find that AA's practice of putting EXPs at the head of the line will more than offset any loss of priority using VIPs over miles. In the last year and a half I've had only one upgrade not clear, out of some ridiculous number of flights.