Dungeon Xp - I find that the rewards from doing a dungeon are only in the main quest. You get the skill point from them and there is no reason to do them again. This isn't necessarily a bad thing on my first character because I enjoy playing the rest of the game without being way over it's level. This is why I haven't done the Alliance War content and do not plan to on my first character until reaching level 50. However, if you want retention with people making alts, dungeons should provide equal xp/time to questing or (even better) mob grinding. I can't remember the last MMO that made grinding mobs an incentive over other play-styles. As it stands, you can expect players on alts to start farming areas of mobs which, with the strange server setup will be a huge problem for new players who have all their quest mobs killed by grinders.

Loot - Overall the loot in the game is not exciting. The difference between a white sword of a level and a blue one (dungeon gear) is about 5 damage. That's nice and you might get 2 points more from the enchantment, but it doesn't change the game. This isn't just in dungeons but throughout the game. If you aren't planning to rework loot tables to all be more rewarding, then you might want to give out purple gear in dungeons. It is nice to get a blue drop, but I don't get excited about it. Often, it is a marginal upgrade of 1 or 2 points over what I have or just something to sell on the guild store.

Grief Protection - Your dungeon group finder isn't designed with grief players in mind. During the beta and right now people are still engaged by a big huge game to explore, but eventually, they'll get bored with it. This is when grief players start to victimize other players and then those other players quit or waste a lot of your money on customer support and then quit when you don't ban the players who grief.

First, the dungeon finder shouldn't add you to a group until a full group is made and at that point, it should confirm that you still want to go. Then those who confirm should be immediately warped to the dungeon they are doing. The reason for this is that currently it would be extremely easy to grief others by joining a group and then never joining it in the dungeon. The leader could kick the griefer (possibly, I don't know how group leader ship works with the group finder), but there is a chance that the griefer might be the leader.

Second, there needs to be a votekick function for the group to kick players. The reason for this is that grief players can ruin a group's run otherwise. They might choose to stop healing, tanking, or dpsing during a fight to intentionally get the group wiped or they might queue as a tank while wearing light armor and having no tank skills for getting aggro or mitigating damage. Additionally, I'm not sure if this is working yet, but players should not be grouped with other players who are on ignore. This is our way of black-listing bad players.

Dungonen Finder UI - the dungeon finder needs a better UI or it needs to just work seamlessly. For example, in Warframe, you choose to go do a mission and if there are 4 other players available, you are grouped. If there are not, then it waits about a minute for some to show up and then launches you or you can choose to launch solo. The game adjusts the difficulty based on the size of the squad that goes. That's asking a lot since ESO didn't design dungeons initially, but improving the UI so that the dungeon finder isn't so nested would be great. This is why people will use the tool. No one needs groups for solo content.

In fact, we are packed in so tightly even in little mission instances, that I feel constantly annoyed that I am always always always surrounded by a hundred other heroes. I miss the isolation of Skyrim. If they had 10 times as many instances and allowed us to occasionally be alone, the game would be much better. . . what would be even better is if all of the solo PvE content was just multiplayer where you invited your friends like in Borderlands then when you clicked on group content, the UI would seamlessly match you with a group. No dropdown boxes. You just choose where you want to go and your class and you go there and play with other people who did the same thing. It's so weird that all of these design issues have really great answers that other designers came up with in other games. . . which scares me because it makes me worry that you are designing without these solutions because someone who is nostalgic for old game designs is in charge - "Modernity and popularity be damned, we're doing it like we did it in Everquest and all them whipper-snappers with their Facebook and their iPhonepads can just learn to spam zone chat and meet someone in town if they want new gear. None of this auction house business!" - Crazy Old Game Developer.

Seriously though, this is your game so you can make it how you want, but PLEASE fix the things I mentioned under griefing. Those are a big deal! I can't believe your beta testers didn't notice these griefing holes. . . then again, that's my fault too. I was in the weekend betas, but I chose to only play a little because they were way too crowded and with such limited play-time I didn't want to start really liking the game and then not have access to it. My guess is that a lot of us fell into that category and whoever you had testing the main game wanted griefing or didn't understand that developers have to design it out or people will do it. They're probably sheltered by other MMOs that do design so that griefing isn't easy and players have tools to combat it. TESO doesn't have those yet and the griefers will take advantage sooner rather than later. I expect this to be the biggest issue for retention in the next few months.