I haven't read any of the "Diana as Goddess" part of the Byrne run (or much of the Byrne run at all, to be honest), so I did not know that he portrayed her as being that powerful.
Frankly, it's more than a little odd that he would do so. Perez put some very definite limits on the Olympians. Hermes had power issues, Ares wasn't able to kill Diana, and two* minor gods were killed by beings less powerful than they were, and Diana was one of the killers**.
The bit about the minor gods is the most crucial, IMO, since that is what Diana would have been. Well, unless she was elevated to the level of the Dodekatheon, but I find that doubtful.
... but, seeing as how I haven't read the relevant issues, I could very easily be wrong.
*-- Well, there was Eris too, but that was more of a suicide.
**Now that I think about it: has Diana ever been refered to as "Godslayer?"