First I'd like to say that I totally agree that the server responsiveness in this game is beyond terrible, and if you play pvp you'll feel it even more than in pve.

But can I ask where you got the idea that the server tick rate runs on a 0.3s clock interval? I have a hard time believing it, else if you just look at how animation delays work in the game, cast times and effeect resolutions at the server side, they would all fall into 0.3s multiples, which they don't (server delays seem to be about 40ms iirc which is in line with your WoW example but I could be wrong on that).

The real problem is how the whole delays and resolution of everything is coded and processed rather than the server tick rate itself, which I think is fine.