Is there a "magic number" for Enchanting, in that you can disenchant everythng in the game (currently 275 for pre-WotLK content)?
My 375 Enchanter was able to start disenchanting blues as soon as I hit Northrend shores, so I can't say for sure what the minimum level is. However, we can take some guesses based on what we saw in The Burning Crusade. As a few readers said, to disenchant epics it actually requires 300 Enchanting. 300 was the profession cap in WoW Classic. Assuming that trend continues, you will need 375 Enchanting to disenchant everything in Wrath. In the expansion after Wrath, it will probably take 450. Getting to 375 is a pretty safe bet.
How is spell damage affecting a Paladin's Ret Aura? Is it reduced like a standard DoT tick or even further? What are the numbers looking like with tested spell damage?
It definitely does not have a high coefficient, it would be pretty wild if it did. Rank 6 Retribution Aura reflects 61 Holy damage. With 0 points in Improved Retribution Aura and running around with 581 Spell Power thanks to Sheath of Light, Retribution Aura 'ticks' for 105 Holy damage. My probably-faulty off-the-top-of-my-head math says it takes just shy of 13 Spell Power to add 1 Holy Damage to Retribution Aura. Someone with a better head for calculation and numbers, please feel free to math this out.
Holy Paladins will probably have a lot of fun with it and every little bit helps Protection Paladins, but don't expect Retribution Aura alone to cause a Rogue to spontaneously combust when he stabs you.
Where are the Warrior glyphs?
Where are most of the glyphs? There are only a handful for each class so far, and there are 0 Minor glyphs implemented. We've been getting a ton in every beta patch though, so I imagine the Warrior ones, at least some of them, are on the horizon.
Has anyone tried to go back to level 70 heroics at 80? How possible would it be to solo/duo them?
This 3-man Karazhan should give you an idea of how possible it will be.
Are we going to be able to buy blank inscription parchment and, if we are enchanters, put spells on it to sell on the AH? Or do we need to be inscriptionists and enchanters in order to sell enchantments?
Enchanters can buy parchment (vellum) from Scribes, no need to have both professions. Word on the street says the super high-end Enchants won't be able to be placed on the auction house, but those aren't implemented yet so we can't say for sure. Most enchantments can definitely go on the AH, as long as you get parchment from someone else.
Does the 51 point Resto talent for Shamans still suck as much as my first impression of it?
Well, that depends on your definition of "suck." Spirit Link is good, but it's situational. It helps distribute heavy damage a bit, which is a good thing when one of your most awesome heals is Chain Heal. You can use it to stop a gib, and follow up with Chain Heal to heal everyone involved simultaneously. In some situations, that's much, much better than one person taking the full brunt of the damage. Do you dislike situational 51 point talents? Then it might suck to you. It most certainly has applications though, and has good synergy with other Shaman strengths and helps overcome a small weakness.
Will my Death Knight have any bags beyond his backpack?
Yes, all Death Knights start with four 12 slot bags in addition to their backpack.
With all of the achievements and titles for completing X quests, is there a way to see how many quests you've completed?
In Wrath of the Lich King, yes. If you're looking to get the quests done beforehand, no. An example of what the panel looks like is just below.