At the moment, Craftworld Eldar could be in a worse spot, especially compared to some of the other codexes. They have a number of units which, together with the ynnari faction rules, allows them to field relatively competitive 'elite-style' armies.
That said, I see two significant problems with Craftworld Eldar. Firstly, they don't have access to a variety of competitive anti-horde units. Secondly, a large number of their units are over-pointed such that they don't see much use at all. With a number of units, these problems overlap – I.e. traditional anti-horde units are too points inefficient to see use.
Taking the lack of competitive anti-horde units first. In previous editions, these would have included the following units – Windriders, appropriately armed Vypers and Warwalkers, guardians, dire avengers, night spinners (and possibly fire prisms) and swooping hawks. None of these units are seeing much competitive play although some are better than others. Personally I think guardians are probably in the best place on this list but they're still not great. I have a few ideas on how to make these units competitive choices. This includes comments on how to address the second issue, overcosted points values:
1. Windriders – They are too fragile for their points cost, especially with no move-shoot-move ability and changes to cover rules. I suggest a points reduction of the base model (no wargear) to 10 points. This will mean a scatter laser jetbike will cost 25 points. If that still doesn't work, I suggest considering giving them a 3+ save again. I don't think it would be good to go back to the 'unfun' jump-shoot-jump rule (even though I love it).
2. Vypers – One problem with Vypers is that you often want to run them as dual shuriken cannon so you can avoid the 'one gun' platform issue. The other problem is their excessive points cost, at between 80-90 points for a single heavy weapon model. I would suggest a points reduction to 44 points per model. They also need a different special rule. Their 'blade wind' ability doesn't cut it and should be replaced. Firstly, it commits you to taking large units of Vypers (that can't split up) which hurts you on satisfying detachment requirements. Secondly, you lose the rule once one of the three vypers dies. I would suggest that they be allowed to move and shoot heavy weapons without penalty. If that's not good enough, in the alternative, give them the -1 hit rule that the venom has.
3. Warwalkers – Again, too expensive. Again, I would suggest a flat points reduction to 31 points per model. Another way to go, perhaps with a less aggressive points reduction, is to give them another mobility 'trick'. I always thought the forge-world 'jump-jet' style walkers were cool. Perhaps give them an upgrade option as follows – "Once per game, at the end of your movement phase, you can move this unit 24" in any direction [insert standard text about not landing with 9" of enemy models etc]". Alternatively again, give them a rule equivalent to 'outflank' from previous editions. Regardless, they need a substantial points reduction.
4. Dire Avengers – Horribly overcosted. I suggest they be 12 points with their weapon. This could also be complimented with a 1 CP 'bladestorm' stratagem equivalent to their previous rules. For example – "1 CP – Bladestorm – Use this stratagem during a shooting phase. Pick a friendly Dire Avenger Unit. That unit's avenger shuriken catapults become 'assault 3' until the end of the phase. A dire avenger unit can only be the target of this stratagem once per game". Given how good horde armies are at the moment, even this might not be good enough. Perhaps a dual firing mode for their weapon could be considered. E.g. mode (1) – '12" range, assault 3', mode (2) '18" range, assault 2'.
5. Guardian Defenders – Make them 6 points base and let their heavy weapons platforms move and shoot with no penalty, just like previous editions. Giving them a stratagem similar to that in relation to the Dire Avengers above could also be considered.
6. Storm Guardians – Storm Guardians have not been playable since 3rd edition (when I started playing) – they need aggressive help to become viable. This is especially the case when they are competing with guardian defenders and the excellent shuriken catapult. I suggest making them 5 points base, with a minimum squad size of 6. This would allow one squad to fit in a falcon and two squads to fit in a wave serpent. It would also synergize better with the ynnari rules. The costs for them to take flamers and fusion guns should also be moderately reduced in some way. Say, 12 points for a fusion gun and 6 points for a flamer. Depending on how powerful those changes are, allowing them to take 2 special weapons only in squads of 8+ could also be considered. Granted, these changes don't necessarily make them a better 'close-combat' guardian unit. I'm not sure how you do that however without making substantial changes to their base strength/toughness 3, 1 attack, 5+ save statline. Perhaps give them 2 attacks base?
7. Night spinners – I would suggest a base cost reduction to 135 points and an improvement to their gun. Perhaps make its gun heavy 3d6 but make its damage characteristic '1'. Alternatively, add a rule to its gun equivalent to – "Any time an enemy unit suffers a hit from this weapon, that unit must halve its movement and charge ranges, rounding up".
8. Swooping hawks – Points reduction to 15 points including their gun. Make lasblasters 'rapid fire 3'. Furthermore, remove their ability to deal mortal wounds and replace it with an anti-horde ability, similar to the swooping hawk grenade pack rule of previous editions.
I have tried to make 'balanced' suggestions on the above units but regardless, changes need to be made to give Craftworlds competitive anti-horde units.
The other broad issue is overcosted units across the Craftworlds index. Notably examples of these include rangers, falcons, fire prisms, vaul's wrath batteries, striking scorpions, warlock conclaves and warp spiders.
To reinforce the above comments on uncompetitive units and a lack of an anti-horde option, one only needs to consider the units commonly appearing in Ynnari Craftworld tournament lists. These are limited to – Wave Serpents, Dark Reapers, warlocks, spiritseers, farseers, autarchs, hemlock wraithfighters, crimson hunters, howling banshees, fire dragons, d-scythe wraithguard and shining spears. Apart from these units, very little is appearing in Ynnari Craftworld lists. Note that none of these units are dedicated anti-horde units. I would suggest that wave serpents are not specialists in this role. With triple shuriken cannon they can help, but their real strength is via providing a durable, mobile transport and late-game objective grabber.