I'm not convinced botnets are a big problem. Sure, CPU mining botnets exist but how nuch mining is actually
performed by botnets and what effect do they have? I never seen any attempt to quantify.

Way back, Vertcoin switched from Lyra2RE to Lyra2REv2 apparently because of botnets. The Lyra2REv2 algo was
less friendly to CPUs but more friendly to ASICs. They then switched to Lyra2REv3 which was also quickly taken over
by ASICs. They might have been better off to stay with v1.

Cryptonight was a more recent botnet scare, miners were being downloaded by web browsers without the users'
knowledge or consent, with all mining going to the web site owner.

But it wasn't until an ASIC arrived that Monero took action and switched algos. ASICs were obviously a bigger concern
for them than botnets.