So if any of you haven't read it yet, you really should check out Zenimax's now very old article on how to run dungeons in ESO.
http://elderscrollsonline.com/en/news/post/2013/07/01/inside-eso-dungeons
The most important thing about dungeons in this game is that there is not a traditional aggro system. Zenimax has an entirely new type of threat mechanic that they aren't fully divulging. It seems that healers draw a lot of threat. AoE's from your DPS will draw a lot of threat.
Most importantly for Tanks, there isn't a whole lot of taunting in this game. The one taunt from Sword and Board is best used if there's one really tanky (non-boss) mob in a room that the tank needs to keep on him. Other wise, controlling a room is done almost entirely through CC. You want an AoE Taunt? Try Dark Talons instead. You can lock down groups of mobs to keep them away from your DPS and healer in the back.
Also read the new tanking guide on TF: http://tamrielfoundry.com/2014/03/tanking-primer/
For healers, I'd recommend not speccing for Heals only. You're really going to want some form of either CC or damage on your bar. The CC is just to keep mobs off of you until the DPS or tank can show up to help. Encase (for Sorcs) and Javelin (for Templars). Damage is something you can do fairly well as a healer in the back actually. I'd go as far to say a healer who isn't also doing SOME damage in this game is hurting the group. For a Sorc Healer, Lightning Pool is a great option even if its your only damage skill. It will give allies the opportunity the pop the Conduit synergy and do free damage to tons of mobs. For Templars, I'd recommend Backlash (both morphs are amazing for healers) as it also enables you to call targets from the back of the room.
DPS is a whole different story. Everyone knows the basics, but the important thing is how you build. You'll want some CC to help the tank, lots of AoE damage, and options to kite and single target for bosses. Its important not to OVER use the AoE though or you will generate all the threat on yourself.
Finally, TeamSpeak communication is going to be key for tough dungeons and eventually Adventure Zones. If you're a healer and you see mobs coming after you, CALL IT OUT!! The only way the Tank or DPS can save you is if you tell them you're in trouble.
