Quote:

I bought a Seagate Firecuda thinking it would be a useful compromise between SSD and platter. Hasn't helped much in this case, to the best of my knowledge.

So this Seagate is your boot drive? How old is it? Have you run Defraggler to check the health parameters? Can you post a screen shot of Defraggler Health tab? Have you checked fragmentation?

Also how much RAM and what is your processor model(be specific)?