I don't really have them too fleshed out but just some ideas I got while at work today.
Lycanthropy
I was thinking about how much I played a druid in Diablo2 and got to thinking it would be cool if they had some shapechanging powers. Other than there being were-forms in this tree I didn't really think it out much but it's an idea.
Martial Arts
Could have a skill that gives you bonus damage and stuff for fighting bear handed. The skill could scale with level as well as with points invested that way it stays viable over the corse of the characters life. It could also implement stuff like the assassin in D2 with finishing moves and stuff.
Look at my idea's they're more or less stuff that I liked from D2 but I do think they could be viable Masteries. If anyone would like to ellaborate on my idea feel free to. Anyway. There's my mind at work.
