For the record: I meet hardly any "pure" robots these days. ("Hi. I'm StinkyBot. spamsize dot biz sent me.") They're still trying, but they get the 403 they deserve, so I don't think about them. It's primarily botnets with humanoid UAs. I could fine-tooth-comb the UA and continue filtering out the spurious ones. But honestly, at this level of detail, with a site the size of mine, it's less trouble to go with IP blocks.
dstiles, there's also one at 5.249.161. But I blocked all of 22.214.171.124/21 (all Sweden) for the heck of it. Oh, and 126.96.36.199/19. Both of those are from recent botnet activity; I pulled the past month and did some more lockouts.
I reserve judgement on two recent ones from 137.135. Look it up :)