It also exist on Squire Unholy Fire secondary attack and Huntress Bling-O-Midas secondary attack as well.
Just noticed the LA version of this bug... splurged it all over the forums. Hopefully it will get some more attention now at least.
The periodic damage from the weapon Glaive of the Storm is also unable to critically hit, not sure if this is connected to this bug, or a bug entirely to itself, or bizarrely out of design.
I can attest to these claims. They still don't crit. On dummies and against actual monsters in maps
EV2 Protonbeam doesnt crit aswell