Although its common practice for malware, they both try to locate and infect vulnerable machines and services (PhotoMiner: FTP servers, Linux.Lady: Redis servers), what caught my attention was this excerpt from the GuardiCore webpage with an analysis of the PhotoMiner malware:
Recent variants of the malware have upgraded this attack by adding
server-side code injection and attempting to install a Linux based
miner.
They didn't went into detail about the Linux variant so I can't say how close it is to Linux.DownLoader.196 used by Linux.Lady. The Softpedia article also goes on about other possible similarities:
Just like PhotoMiner, Linux.Lady comes with self-propagation features.
The trojan includes a function that detects the IP address of the
infected computer, scans the local network, and probes for other
vulnerable Redis servers that don't feature a password on the admin
account.
About how much of the hashrate is dominated by botnets I would say its minimal:
My view is that botnets "dominating" mining, after working out
reasonable assumptions about hash rate of the network and of bot
nodes, would require many hundreds of thousands to millions of botnet
nodes and if that were going on, it would have a huge visibility
footprint. Since no such thing is visible, it almost certainly isn't
happening. Smaller botnets exist.
source: https://www.reddit.com/r/Monero/comments/4rpcbl/are_there_any_known_significant_monero_miners/d53i6i7
And he was proven right.
As we can see malware like these (CPU-intensive) are spotted pretty quickly, but as there are a large amount of unprotected and unattended machines over the web your guess is as good as mine.