IAs are random Kill Quests (sometimes Gathering) which are in the open-world. It basically gathers up to 20 people in a given area. It will teleport you to the "general" area, as well where you should be questing. Instant Adventures are based off existing quests already in the game, so you'll see the same quests eventually just by doing the quest chains.

The quest is shared between all members, all their participation counts towards the end goal. At the end of an IA Quest run (which is usually 4 to 5 quests, you get a mini boss fight, and then the quest chain starts to "loop over again", or random-ize. You get boosted experience while doing this.

The downside with doing this is that if there are numerous amounts of "new players" calling you a bot, they can actually vote you out of the group. You'll usually get a "Bot get out" and followed by a vote to kick on your alts to kick your main or one of your alts out. By this time i usually have enough time to vote kick the whiner out with my alts before another one gets kicked. This by far is very annoying. As we are not hurting anything since multiple IAs run at any given time if there is enough people.

As far as boxing IAs (when doing so without being troubled) any combo of classes will work. Just be aware the "mini-boss" fights sometimes require a tank or good enough to bounce aggro between non-tanking classes, or have enough heals to keep up someone with the damage. Because some do hit hard depending on which one it is.

As for your 5 mages, that may not be so bad, the Harbinger (Melee Mage) is F'ing amazing, hence why i wish my second rogue was another Mage, and apparently Harbinger/Chloros are really good melee healers (i have no proof or witness of this personally).

I reactivated my accounts from work just a few minutes ago, and will probably start playing again around my Minecrafting. Im currently Wolfsbane with a decent Raiding guild (when i was active), but i may come back fresh and find a new guild and server.

.... As for Dungeons, i like a lot of the new dungeons, i got my toons to 56-57 before the baby was born. Old dungeons were fairly do able on Expert Mode (Heroic Mode), with a usually Trinity setup. I do not know the box-ability of some of the newer dungeons. I myself pretty much enjoyed 5-boxing the game. I didnt dungeon run, i primarilly used my toons for crafting and leveling. I did solo play a bit when i was 50 with my cleric as my main. So my cleric at current-50 era raid tier gear right up to expansion. A lot of the gear does come from grinding dungeons out, but go figure like all the other MMOs of this style.

I guess the gear roller coasters was one of the reason i didnt see myself jumping back into rift when my baby was born. But, its still a great game, but then again i still like WoW (Not so much the way it is now), but i like wow for what it was.

Also note that their really is not faction barrier anymore, except in main race cities of (Meridian or Sanctum). You can be guilded/raid/quest/dungeon/PVP with the opposite faction now days.