So from what we know so far about the Revenant is that we know they channel heroes to change up their role in battle and style of combat. We also know they channel the powers of the mists. Similar to what powered the Ritualist back in GW1. The more I read and look into it the Revenant sounds similar to the Dervish in terms of its mechanics. Someone else said they sounded like a Dervish, but at the time I felt they were jumping the gun a bit too fast with it. But it would be interesting to see a hybridization of the two. Thematically the ritualist has been missing from the game and mechanically the dervish was missing as well. So this could be really nice.
Here is what the heroes sound like to me. http://wiki.guildwars.com/wiki/Form
Do note that forms in GW1 worked very differently then they do in GW2. Be sure to check out what they did for the profession. You can ignore the non-dervish related forms.