The Elder Scrolls Online Preview and Gameplay Footage

Dawnguard wasn't the only Elder Scrolls title showed at E3, with The Elder Scrolls Online also being demoed for the press, and while it's not available publicly for us to see, we can still at least read the reports on it, like this piece from RPGFan:
TESO also features plenty of standbys from the MMORPG world, including instanced five-man dungeons, which will also have heroic modes for high-end players. Along with that will be raids for guilds and a very interesting feature: public dungeons. These dungeons won't require a group, but they'll have significantly more difficult enemies than those aboveground. Players will have to assist each other for maximum efficacy, but you won't have to stick with someone beyond any single encounter. As well, rewards will be shared by all players involved, not unlike public quests in WAR or rift encounters in Rift.

All of this will be done via action-oriented combat which features the three standard resources found in the Elder Scrolls: Health, Magicka, and Stamina. Different abilities require different resources, just like the core Elder Scrolls titles. Block costs you stamina, magic requires magicka, and everything else falls into line. Each character class also has a different role, so players will never be left out of any group.

Interestingly enough, your party isn't the only group with a balanced build: enemies have groups with their own dynamic. Our demo featured a tank with a necromancer and a healer it was most effective to kill the necromancer first so that he wouldn't resurrect fallen comrades as skeleton warriors. Should you do well with these encounters, the game rewards you with things such as additional loot.

Additionally, G4TV is offering a "gameplay demo" with creative director Paul Sage with quite a bit of footage. We don't really get to witness combat or the interface, but it should at least give a better feel for the art style and environments.