Djinn to are a bit underpowered...
Their cost and ability cost are too high for a card that works ONLY with another specific card, that isn't even of their element...
I think you have 4 ways to make them good:
1) Lowering both their price and ability price. (something like cost 5 and ability cost 2/1 for upgr. version)
2) Making their skill work with ALL fire creatures.
3) Making their increment on phoenix permanent (and not just for one turn).
4) Giving them a lot better stats
That couse they are expansive, have not all that good stats, and their ability is very expansive...
To play with them you will need A LOT of Wind Pillars, and who will put about 10-11 wind pillars and 3-4 djins (so 15 cards) only to have a +2|0?
As they are, I'm not even sure they are worth in a phoenix specific deck, and they are no worth for sure in any other deck.