Yes, and no. Having a design that isn't trivially easy to model can be a good thing, because it promotes experimentation and discussion instead of just being a solved problem. I have seen a lot of theoretical discussion about how a simple talent like Incite works, and that's the kind of thing that keeps the theorycrafting portion of the community engaged.
What we really don't like, somewhat ironically, is simple but hidden math. When there are two talents and one is a 10% dps increase and one is a 5% dps increase, and every savvy player knows that intuitively and every beginner gets caught by the "trap," then that's not cool. Armor penetration was just a god stat for many classes, even though that might not be apparent without some kind of insider knowledge. If armor pen had a slight edge over say crit in some circumstances with some gear levels and some talent builds, then we probably would have kept it. It becomes an interesting decision instead of a no-brainer.
Vanish (Source Vanish needs its improved stealth back.)
This is correct, provided you aren't using Hunter's Mark or some kind of "I still see you, dude" ability. If you have a rogue targeted, and they Vanish, you should lose your target.
This is the case in beta as far as we know. There are some situations on live where it does not work, but they are all fixed in beta and therefore will be fixed when the Shattering occurs.
As I said before, make sure when you're reporting a bug that it is a legit bug and not "I wish Vanish made me immune to spells because that was cool when it worked even though it didn't work often."
EDIT: Faerie Fire should prevent you from using Vanish. If you use Cloak of Shadows to remove Faerie Fire, you should then be able to Vanish. It should not make you waste the Vanish cooldown and it should not let you Vanish but let the druid still see you.
vanish removes hunter's mark
We have changed this (Hunter's Mark behavior) back and forth quite a bit, so I'm not comfortable at this point saying one way or the other. Excluding a few cases like this though, Vanish should work as described above.
Slam (Source Arms Rage Concerns (PvE))
If you're the kind of warrior who just doesn't like Slam or think it should scale with haste, that's fine feedback to provide, but not the kind of thing we are going to change before Cataclysm.
If Slam isn't worth using for a level 85 Arms warrior in reasonable gear, that's a problem. "Isn't worth using" means that it isn't a dps gain to use Slam, not "I don't like using it."
Arms Rage Starvation (Source Arms Rage Concerns (PvE))
If Arms at 85 in reasonable gear doesn't have enough rage to hit Mortal Strike, Slam, Rend, Overpower and Colossus Smash nearly every time they are up, then that is a problem. Things like shouts and Deadly Calm should cover up a few rage gaps, but in general you shouldn't be standing around waiting for enough rage to Mortal Strike again. If Arms can't always hit Heroic Strike, that is intended.
Rage Generation Balance (Source Arms Rage Concerns (PvE))
We felt that for the high-end Lich King PvE warrior that rage was largely irrelevant. You could hit whatever buttons you wanted to when they were off cooldown. If you put electrical tape over that red bar, your gameplay wouldn't change much.
In Cataclysm, we want rage to matter. We want you to have the gameplay of managing a limited resource. We want the electrical tape scenario to make the game almost unplayable for you.
It's easy to take that to extremes. We do not want warriors to hit say Mortal Strike then have to autoattack several times before they have enough rage to hit Mortal Strike again. Standing around waiting too long isn't managing your resource -- it's just standing around (assuming you didn't blow your rage through poor decisions generally involving Heroic Strike).
However, when I write stuff like that, it's easy for players to then say "Aha! Any time I can't hit my abilities on cooldown, then my rage income is too low," meaning that they are trying to get back to their existence not being limited by rage again.
That's why I said "nearly." Are there going to be moments where you avoided a lot of damage or had your damage avoided or were in the middle of moving or (heaven forbid) wasted rage on something that you shouldn't have? Most likely. In those moments, use something like Berserker Rage, Deadly Calm or Battle Shout to get a little rage. But you shouldn't ever feel like you're in a position to take say Slam off your bar because you can just never afford it.
Slam's balance is also tricky. We nerfed its damage at a time when beta warriors were considering not using Mortal Strike at all. But Heroic Strike should never look more attractive than Slam for Arms. Heroic Strike is for times when you've hit every button and still have rage. We realize with certain amounts of haste that Slam may eventually fall behind, but we don't think we'll be there in the first tier of content so we have time to evaluate how the rest of the mechanics and abilities are working before we make any changes there. If we're wrong, and Heroic Strike does fall higher in the priority than Slam for Arms, then we'll nerf one or buff the other.
Haste (Source Arms Rage Concerns (PvE))
The actual explanation is that haste (in Cataclysm) gives melee more resources, and all of our melee (though Ret still the least) can often do more when they have more resources. To use your warlock comparison, the lock can cast faster (i.e. "do more") with more haste. Warriors already have that, because haste gives them more rage, which lets them hit more buttons. If haste provided more rage *and* more damage, then there is a chance that melee would scale better than casters and that haste would trump every other secondary stat (except possibly hit) for Arms. (By contrast, giving warlocks more mana over short time periods wouldn't really do anything for them.)
It's definitely possible that haste isn't good enough for Arms yet, but we want to avoid it slipping into the master stat. We might be able to make say Rend or Slam scale very slightly with haste to make up the difference. It will be confusing if some melee attacks scale damage with haste and some don't, but that might be the lesser evil.
Rage Cap (100) too low? (Source Arms Rage Concerns (PvE))
I don't think that's it. We just like the design (of rage capping at 100). Usually when players want deeper pools, they are asking for more slush room so that they don't waste resources if they unexpectedly get more than they could handle or didn't get to spend it as efficiently as they anticipated. But that's part of the challenge of the resource. You have to keep the max in mind and base your decisions around not wasting it. Procs (of all kinds) get wasted all the time, by almost every class. One of the marks of skill of good players is trying to minimize that loss, and by extension, knowing when it's okay to take that hit.
Remember, our goal isn't necessarily to try to make things as easy as possible for you.