@Yorga Warriors of Chaos gain Reign of Chaos. Beastmen gain marks, eye of the gods and Reign of Chaos. Daemons get a better Reign table, but become unstable instead of instability, which has its pros and cons. So Chaos is gaining more than Undead Legions. There are some strong combos we are starting to see too, the Beastmen Braystone with Chaos Wizards being one of them.
Elves get a lot of synergy and power. All their Army special rules are plain better and most of the units cover the weaknesses in the other armies. With that said, the elves are all still T3 everywhere, so that weakness is still there.
Dark Elves even with T3 can dominate most armies. The one main type they cannot is armies with a plethora of 1+ armor saves. In steps the wood elf 'allies' and problem solved.
The book is much more reliable and doesn't kill your troop.If you add the 4D6 magic and spell spamming to the equation, a Book of Hoeth bearer will dominate any game. T3 getting you down? Spam flesh to stone. T7 in no time. It's only a mere 8 to cast. Super reliable with two dice and book. You only have to toughen up the troops in combat or who are about to be charged. I own fully painted High Elf and a Dark Elf armies. Having to really fight my urge to make the super army. It would be nothing for me to add a couple of Wood Elf units to my collection.