From what's been revealed so far we have a general idea of the format of the masteries. For example the Zealot has Alchemy, Witchcraft, and Ritual masters which focus on healing, buffs/debuffs, and damage respectably. The sorceress has a nuking, aoe, and dot/debuff tree. The Chosen has tanking, aura/magic, and damage trees. So it doesn't seem too unlike wow in the beginning.
This dev chat gives a little more information.
Brannoc - *[M]Tree* How many Career Mastery abilities/skills/spells are there in each tree? Also is there only one Moral ability per tree? If not what ranks will the moral abilities be?
[WAR]Gersh - So remember the first thing Career Mastery does is effect some baseline abilities you get normally while leveling
[WAR]Gersh - Each Mastery Line will effect around 5 - 7 of these base abilities.. Increase the mastery level and the level of that ability will also go up
[WAR]Gersh - Beyond that each of the 3 Lines have additional rewards
[WAR]Gersh - 3 Specialized Abilities that are more focused and more powerful then base
[WAR]Gersh - 3 Specialized tactics
[WAR]Gersh - and one Tier 4 Uber morale
[WAR]Gersh - Best morale abilities in the game come from mastery
So again very similar to WoW, focusing on a lot of passive buffs and giving a few activatable skills. One thing to note is that some of the passive benefits of a tree are through tactics, which means there is an opportunity costs. This may hinder cross speccing a bit as tactics from one tree will be competing for slots from another.
What I'd like to know is the relative amount of "talent points" characters have to spend, are there enough for 1.5 trees?
Perhaps some posters, who also happen to be in beta, might share some "rumors" they have heard.