First off, Death Knights. Depending on which spec you chose to level in, the proposed changes could end up having a very significant impact on how you approach leveling your Death Knight. I personally leveled my Death Knight using a blood spec, so with the switch to blood being the dedicated tanking tree, it's going to presumably require a switch to either Frost or Unholy for leveling. I'm assuming here that you are leveling through questing, and not through the Dungeon Finder. If Dungeon Finder is your preferred leveling method, then by all means, stay blood and tank away! Having all the tanking talents in one tree should make that much easier for starting Death Knights.
The changes to the rune system, if balanced appropriately in terms of the overall damage, don't seem like they will have much of an impact. I may not be pushing quite as many buttons because of the resource constraints, but if you believe what they've said so far, things should go down just as fast.
I do think it will be an overall negative to DK leveling to not have all of the self-healing abilities of the blood spec combined with pretty hard hitting damage. That made the class a leveling machine, and if you give those up for just straight dps as either frost or unholy, the lack of self-heals is going to make it a little bit more challenging. Overall, at least at the moment, I don't see a clear leveling winner between Frost and Unholy, so it looks like it's a "go with whatever you like".
Rogues - as if leveling a rogue wasn't fun enough as it is, we're now getting a healing ability:
"We would like to improve the rogue leveling experience. Positional attacks and DoT-ramping mechanics will be de-emphasized at low levels and then re-introduced at higher levels for group gameplay. We are also providing rogues with a new low-level ability, Recuperate, to convert combo points into a small heal-over-time (HoT)."
We'll also be apparently picking up the ability to continue to use the combat points from recently killed targets for non-target specific effects like Slice and Dice and Recuperate:
"To complement the change to combo points, non-damage abilities such as Recuperate and Slice and Dice will no longer have target requirements and can be used with any of the rogue's existing combo points, including combo points remaining on recently killed targets. This will not affect damage abilities, which will still require combo points to be present on the specific target you want to damage. To coincide with this, the UI will be updated so that rogues know how many combo points they have active."
And as another bonus, if you're leveling as combat swords, you can now Ambush!
"Ambush will now work with all weapons, but will have a reduced coefficient when not using a dagger. When opening from Stealth, all rogues will be able to choose from burst damage, DoT abilities, or a stun."
Looks like a lot of abilities (except for Backstab) are going to have their weapon related limitations removed - so Hack and Slash will work whether you're using sword, axes, maces or daggers.
All in all, great news for those out there leveling rogues. Should definitely provide a lot more flexibility in how you choose to level, as well as increasing your overall survivability - always a plus.
So that's it for those two. Tomorrow, I plan to finish this up with thoughts on Hunters, Druids and Mages.