My main opponent in my gaming group is an eldar player. I learned to hate them really, really hard. Nearly everthing I can do with my Marines, they can do better (beside an all out drop-air list, but that is unfunny to play for both sides). So just a few comments:
-Vampire: This aircraft is excellent to shift priorities from one side of the field quickly to another. Mainly used to reinforce an flank sweep where the enemy shows a weakness to completely break up a flank. He often uses it in combination with a flight of Nightwings to suppress AA or eliminate enemy aircraft.
-Stormserpent: The only unit I cannot say much about. My opponent sees them as "very" unfluffy and simply refuses to use them. (Driving Wraithgates, yeah, for sure

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-Windriders: They are a pain to combat. Fast, hard hitting and if they begin to win assaults they are faster than a greyhound on speed. He usually works with combinations of 2 and one Falcon unit to soften up the target. my only chance usually is to get them early with air-ground fire or long range attacks, which you would better use on jucier targets.
-Aspect host: usually the all out neck-breaking unit. Held behind a screen of fast units it heads for the heart of the opponents army and usually crushes ist very effective with some combined assault-help. I´ve only seen them dying once in an assault. (Against my Minervan Infantry Platoon in a two round assault where the Commissar-stand killed two units alone

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-SHT: Support units to fill gaps. Two nearly fix MW kills is enough to justify them, cobra simply is a TK-monster...only used against orks and SHT heavy armies (Minervans?

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To summarize it, Eldar do not need the spirit stones. They are fragile, sure but I rarely see them loosing exept bad luck or a surprise army composition. They have enough tools to deal with everthing you throw on them....this is epic-proven, ask my Marines and Minervans
greetings
RS