Wilderness - accepted that the IPs used by yandex are a mess - generally two or three per /24 or several small groups within a /24. A few days ago, in an attempt to coax them into a more extensive coverage of one of my clients' sites, I enabled almost all yandex IP ranges completely. I also added a few more UAs - their list of bot UAs on their site is very good and a model to various other bots I will not mention.
For reference, the yandex ranges I have are as follows (most though not all of these are RU):
18.104.22.168 - 22.214.171.124
126.96.36.199 - 188.8.131.52
184.108.40.206 - 220.127.116.11
18.104.22.168 - 22.214.171.124
126.96.36.199 - 188.8.131.52
184.108.40.206 - 220.127.116.11
18.104.22.168 - 22.214.171.124
126.96.36.199 - 188.8.131.52
184.108.40.206 - 220.127.116.11
18.104.22.168 - 22.214.171.124
126.96.36.199 - 188.8.131.52
In the past I have run rDNS checks on the IP ranges to extract bot IPs but their system is too volatile. I figure that a valid bot UA on any of these IPs is probably valid.