Hum, you do realise this post was about pvp, ay?
Yes. As far as I can tell, the biggest controversy about Nymphs being strong, or even viable in PvP is the rarity. If one could simply go out and buy one, it wouldn't be as much of an issue.
The fact that you need to get lucky with the oracle to get a Nymph, is the main reason Nymphs are so rare.
As far as my thoughts concerning card rarity and how much it affect element power, is thus: Let's say a mono element deck, needs to have X or Y card to win. X card is readily availible, but Y is a rare. Now, let's assume mono element deck based on X card has different strengths and weaknesses than mono deck based on Y card. Basically, a newcomer wanting to do a mono element deck would have to base it on X card. Whereas someone who's been playing a while could do a X or Y deck.
Then again, maybe I'm outdated as all get out for thinking mono element decks are viable, and need to learn duos and rainbow building eh?