Suggesting this because I think the upped fire nymph is worse than unupped. Either the upgraded one should be buffed, or the regular one nerfed. It might not be an issue if you always assume it will only ever be played with a shard of readiness, but I'm not assuming that.
Right now, if you use the rage skill 3 times on upped, it's the same cost as 4 uses on regular (12 fire cost for the skills).
For 12 fire the regular card gives you:
4 times +5/-5. Against opponent that's potentially 4 dead creatures, or -20hp total to a big one. On your own creatures, that's potentially +20 atk total, and easier to use at all (ie, without killing your creature) due to only losing 5hp instead of 6, which makes it usable on more of your own creatures.
For 12 fire the upped care gives you:
3 times +6/-6. Against opponent that's potentially 3 dead creatures, or -18hp total to a big one. On your own creatures, that's potentially +18 atk total, and harder to use as it kills most creatures (even a number of upped dragons) that hasn't been grown in hp.
I suppose the regular is slightly more defensive, and the upped is more offensive in nature based on it's likelihood of killing the target. The upped card has +1 hp as well, but I don't view it as important (although it is needed to use the +/-6 rage on itself).
//-Also, even the regular upped rage potion is the same cost as unupped (3 each). So decreasing the usage cost on the upped nymph makes it similar to the rage cards.