In the gunship fight the cannons should be able to kill the rocketeers in the back. Seems to be either a rendering issue or just a simple script issue.

Not able to kill them, not a big thing but not as it should be.

I've watched a video with this encounter and it seems you are right.
However, this is a minor issue that doesn't really bother anyone - I would even go as far as calling it a Storm-WoW Gunship feature, unique to us.