The quote from the fixed poly spell "Nor can you turn into a variant form of a creature. For example you can turn he subject(sic) into an ogre, but not a half-dragon ogre." is somewhat misleading in my opinion. You cannot poly yourself into a half-dragon no matter what, because it has the type dragon, and you cannot assume any form with type dragon.
I think what the spell istrying to say, is that if you can normally turn yourself into form/shape "A", that does not automatically imply you can turn into form/shape half-A/half-something else.
As a counter example to the half-dragon ogre, a celestial ogre (if such a thing existed in your campaign) would be of type large giant, and you should be able to poly yourself into it.
As to the HD advanced creatures, I was really talking about size advanced ones. If a large gargoyle is just an older medium gargoyle, then you should be able to poly into a large one just as easily as into a medium one. Of course, you'd turn into an average medium or an average large one. If you cannot do this, then using greater wild shape to turn into a dragon (shifter level 7) would be really limited because you would only be able to assume one size category of dragons.
- Z Y G