Hey there,
Personally, I'm not a fan of Guardians. To me, they're sort of like Imperial Guard troops, but more expensive. I'd switch to Dire Avengers, if you can. Rangers are good, but I'd try to find a way to increase that unit to 10 models.
10 Fire Dragons seem a little excessive. Not many things need 10 Melta shots to take out in one phase. I'd shrink the squad down to either 5 or 6. An Exarch with Tank Hunter is a good addition, but you can probably do without the Firepike. Get them a Wave Serpent, so that way you can more easily get within range of your Melta weapons.
Additionally, you're still a little light on transports though, which can be problematic. Eldar have arguably the best Dedicated Transports in the game, so take advantage of them if you can. Otherwise, the rest of the list looks pretty good.
Good luck!