You are correct. They still haven't fixed it on this server?
The Fire Pet is also not supposed to instantly have damage shield as soon as it is cast, although I'm quite fine with that not being fixed (or has it been)?
The link you showed doesn't talk about water pet immunity, though.
On Allakazam's Magical Realm I constantly posted Magician guides since early 2000 that talked about these things.
Here's one I found from 2001 where I specifically talked about the Water Pet's fast regen and poison immunity -
http://everquest.allakhazam.com/db/c...00662102725701