I have already experienced this.

When I started coding up bitprices I was initially using a locally running instance of the toshi server.  It took something like a month to get to May 2015 and once it started hitting the spam attack days, things just slowed to a crawl with some blocks taking 10+ minutes to verify and I soon realized it would never catch up at that rate.  So I shut it down and switched to btcd instead.  Toshi was running on a fairly beefy server:  16 core, 48 gig ram, Raid 1 7200 RPM.     It turns out the limiting factor was the disks and SSD is now recommended for running Toshi.

I realize this is somewhat apples and oranges with bitcoind.   But I wonder if toshi would even keep up on SSD with 2+ mb blocks.