To fix Wood Elves, you could go a couple of different ways...
The rules for big blocks of hoard troops are one of the elements that many WE players find it difficult to compete against. The WE one has archers that can feasibly take advantage of that rule and it's not really to their benefit. I haven't crunched the numbers, but HE seem to do this better.
To address this, WEs can have more (core) units that can adopt a hoard formation, armed with spears, sword and shied, two hand weapons, or great weapons. I think glade guard should have a couple of options other than just bow and arrow. Even HE have mixed bow and spear units and I think WE could have this as well.
Another option is to have a new rule that negates hoard or rank bonuses. Perhaps WE don't need extra ranks to negate an opponent's rank bonus when attacking on the flank or rear. Another idea is that WEs can create flank units out of their parent units, like every army could do in previous editions after winning a round of close combat.
WEs are over priced. Lower the cost of just about everything in the book, especially cav.
WE magic is fairly limited. In addition to making a more competitive WE only magic list, I'd give them access to Beast, Life, Light and Shadow.
I don't mind the dryads right now, but I would get rid of the vulnerability to magic (same for the treekin) and give them the option to rank up instead of being skirmishers.
Since Dark and High elves have pretty powerful rules in Always Strike First and Hatred, I think the WE need something too. Perhaps the army could gain a feigned flight rule (even models on foot) or the entire army can rally, even if below 25%. Another idea is that the army gets a "first round frenzy" rule where they get a bonus attack in the first round of combat but are not subject to the penalties of regular frenzy.
I'd give Wardancers the "Shadows Coil" dance back to end combat as a stall maneuver. I know that's powerful but giants still have yell and bawl.
The current list doesn't have any "warmachines" or even chariots. Some sort of ambushing style warmachines like spiked logs swinging out of the the woods would make since thematically, but might be difficult to draft rules for. Personally, I don't think chariots or bolt throwers are too far out of character for the WEs, but catapults, cannons, and mortars don't fit in at all.
A lot of players like big monsters and every list seems to have one or two in their army. Tomb Kings have a decent list of models on chariot bases, like the Necropolis Knights / Sepulchral Stalkers, that fit into the special selection and have multiple attacks/special rule. A new mid-level monster rider wouldn't break the theme of the army or be totally out of line. Imagine a WE riding a wyrm or bear into combat.
Just my two cents.