wiki is wrong, i get attacked by wolves in both normal and beast form. also good luck trying to fight a giant in beast form, you have no armor and at higher difficulty and level you will get kilked with 1 club swing.
Giants are actually pretty easy in Werewolf Form. Just knock them on their ass and tear them apart. The Mammoths however, are a much bigger pain in the ass, since you can't ragdoll them and when they swing their head and tusks side to side, it can hit you even if you're to the side of their body. The Sprinting Power Attack of the Werewolf is just horrendously powerful though, if it doesn't bug out and cease to go off that is.
http://www.youtube.com/watch?v=trf6hLzn6Ig
http://www.youtube.com/watch?v=qNSDcxQl-Z4 (Fight vs Giants at 5:20)
High level Dragons, like Ancient Dragons, are just plain suicide in Beast Form. They can do 300 Damage a hit on Adept, and 600 on Master, while the Werewolf has no Armor Rating... Not even my Lvl 68 Nord Warrior who has 650 Health/420 Stamina in Beast Form can take them, when he can quite easily beat them in Human Form.