Regarding as to whether Dol Guldur should be destroyed or not, I think that a destruction of the fortress could prove an opportunity to finally show off Galadriels awesome magical abilities.
Galadriel has always been one of may favourite characters because of her enigmatic and mysterious appearance. Especially in the Fellowship of the Ring movie, one could really sense her to be ancient and powerfull without showing off too much.
I cannot remember reading it in the books but according to this lotr wiki (http://lotr.wikia.com/wiki/Galadriel), Galadriel was the key to destroying Dol Guldur.
Now that would be an awesome scene to watch.

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But now he has a mind of metal...