Bit later than I expected, but I finally have a bit of time to talk about the new Demon Hunter class, with a focus on Vengeance.
I didn't really get a chance to play with their abilities proper at the BlizzCon demo, but they - and my respective thoughts on them - are as follows, according to the amazingness that is Wowhead:
Hateful Strike is an ability which deals increasing physical damage as the target's health is lowered, costing 30 'pain,' an as-of-now unheard of resource. Presumably, pain will be generated when taking damage, but I haven't seen any real information on it just yet. When I actually did the demo, I gave the feedback that I'd like it if the demon hunter's playstyle changes a bit with your enemy's health. I found this later, and I can't help but feel a bit happy. If this follows through with some more meaningful differences in playstyle, things could get very interesting for Vengeance.
Fel Blood is a LONG (and by long I mean 15 minutes long) cooldown where 40% of your damage taken is converted into fury, your spender resource. Duration of 5 seconds. Aside from a sliiiiiight need for tuning changes, this is pretty much what I thought Demon Hunter tanking would be like. You take damage, shrug it off, and laugh evilly as you start murdering the guy who thought he could hurt you so easily. If Fel Blood's core mechanics don't change, it has a lot of possibilities down the road when we get more information on Vengeance's full ability list.
Voidblade deals notable shadow damage and heals you for the amount of damage you dealt. Pretty simple, pretty expected. This is a fury spender (and spends 65 fury, specifically), so it's going to combo well with Fel Blood for a LOT of self healing. Once every 15 minutes.
Metamorphosis is perhaps going to be one of my favorite long cooldowns in the game. You get full fury and full health, and you take 60% less damage at max health, gaining even more damage reduction as you drop in health. For 15 seconds on a 2 minute cooldown, this thing is going to be a very highly-pressed button.
Also, it turns you into a demon, what's not to like about that??
Getting to play around with the Demon Hunter was an interesting experience. Their dash was really fun to use and felt a lot like a more visceral roll. Their glide was a bit less useful to me personally, as you can't trigger it while mounted. It's a really cool ability that I'd have loved to use a bit more, but I didn't feel like dismounting and remounting was practical most of the time. Being said, doubt it's designed to be the Demon Hunter's principle travel method, so whatever. Spectral Sight, if any of you watched the demo of it, reduces your movement speed, which to me felt very awkward. I get WHY it's there, thematically, but I'm not sure it really fits the Demon Hunter. My understanding is Spectral Sight is how Demon Hunters see all the time. They see magic and life energy, not the physical. It's just not something you have on all the time because that'd be very annoying for the player.
That being said, I don't know if I'll be going Vengeance in Legion as a main. Certainly as an alt, but I'm looking forward to playtesting the Brewmaster changes. That's going to be very interesting.