Wait, I don't completely get the maths here, sorry ???
The new Light Nymph heals you for 10 hp and makes your creatures bioluminiscent. You can still use it with Hope, it has the same hp, it only attacks less, but now it heals. I don't remember how much was the attack nerf, I guess 7-8 (which is a LOT), but you still heal for 10, which is more (yeah, I know it costs 4/3 
per turn, but healing on a stick is not free). So, now your Nymph/Hope deck has stall instead of attack... Just change the strategy, I can count 3 deck ideas that could work with it (2 of them with Hope, but that's not the discussion right now), and I'm sure that one of them works pretty damn well. I guess that if you don't use it any more is just because you don't like it any more.
Math is very easy.
1 situation:
You have 50 HP and Light Nymph. You use skill and have 60 HP. Your opponent has got for example simple Abyss Crawler 6/6. When he attack You have 54HP.
2 situation:
You have 50 HP and Purple Nymph. You use skill on the same Abyss Crawler. He didn't attack, and heal 6HP. You have 56 HP.
As You see Purple Nymph heals more than White Nymph for the same ability cost. What is more, when You use it on dragon then difference is bigger. Only games with <5 attack ALL creatures (very rare...) makes White Nymph better.
Bioluminiscent? With which card is compatibile? Pegasus? No. Archangel? No. RoL? No. Maybe Crusader? No... Only Light Dragon can get this skill. Sorry, but this card is good for other elements (for example Life), no for Light. Life Nymph has got perfect synergy with life creatures. Light Nymph hasn't got synergy with light creatures... Here is a problem. So this card is useful very very rare.
When You say that losing 8 attack and giving 10 heal (for 4/3 ) is a kind of buff I can only smile 
So maybe we should make Light Dragon as 1/12 creature and gives him fantastic heal ability? Light has got enough heal cards. Light needs attack creatures, no heal 10HP more each turn which cost 4/3 (when 20 heal for Life cost 2).
And at the end - when You think that Light Nymph is pretty cool like Gravity or Purple I wish You good luck
Huh, let's adress this to make it more simple:
1- Never said Light Nymph was cooler than Gravity or Purple one, but also remember that both of them have their drawbacks (because neither of them is OP)
2- NEVER said that losing 7-8 attack and giving the heal was a buff, I actually said it was a nerf! And healing is another strategy. If my dragon attacked 10 points less but healed 15
for free (that's why the nymph was nerfed, bc of the cost), I'd see it as a buff.
3- You can use the Nymph with Photons, but mostly, you should go duo with Life... You say Life has no synergy with it?? See rustler?? Well, each Frog now produces 1
, then each 1
turns into 2
, add in Hope and you're done.
4- Roughly comparing the Light Nymph with a Purple Nymph is like comparing oranges with pineapples, and saying oranges are better because they're cheaper (just a metaphor, not to be compared with ANYTHING elements-related). If you had a Hope shield up, and at least 1 or 2 vanilla creatures, I can assure you, the Light Nymph is better. Purple Nymph is cool in many times, I know, but it's balanced, so you can counter it: It has low hp, can't work without creatures or with immortal ones, your opponent can kill his creatures or AM them back. So, you're just saying the good part of one card, while Light Nymph really pwns with Hope.
5- You can have only 6 heals, that's why it costs less (it's a widely accepted mechanic, it should ALWAYS be like this), while Light Nymph can heal you until your opponent decks out.
EDIT:
Nymphs don't have to synergize with there own element. look at water, and to a lesser extent fire.
True.
