I narrowed down my list of addons to "must haves" only for Jund so figured I'd post here.
From the ones that come pre-packaged with RoR:
AutoDismount
PotionBar - Displays the best of each type of potion in its own separate bar
From Idrinth's DLs:
BagOMatic - Organizes your bag. (Type /bom for options or just use the gold bag icon)
cmap - Minimap with larger square viewing area. (Type /cmap)
Deathblow - Displays a message when you get a deathblow, or someone kills you, and keeps track of kill stats. (Type /db)
Pure - Nice customizable unit frames for yourself and targets, and shows a separate healthbar above the head of the person(s) you are targeting. (Type /pure)
TidyRoll - Makes the loot popups much smaller so they don't interfere with killing. You can left click to need, right click to greed, middle mouse to pass. (Type /troll)
Enemy - Enemy is a very large addon with a variety of functions. Most importantly it changes the group/warband ui to a cleaner and simpler version showing important combat marks like Healdebuffs and Guards. Other features include a Guardtracker, overhead markers for players, combat log tracking and Killspam. It also has the most reliable unit frame frames for party and warband for RoR (in terms of updating when they should). You can turn off the features you don't need. (Right click on any Enemy UI element to configure.)
Honorable Mentions:
BuffHead - Buffs and debuffs displayed over peoples heads
EveryBodyGuard (requires Squared to be loaded)
Map - Full map that comes up when you click the minimap that doesn't take up the whole screen (can resize)
Miracle Grow Remix - Necessary if you do cultivating. (Benefits from the CraftData.lua found here)
Crafting Info Tooltip
Queue Queuer
TidyChat
WarBoard
WSCT (Warhammer Scrolling Combat Text)
Motion - Works perfectly for Talismanmaking according to Gorm. To get some of its functionality for Apothecary, here's what I do:
Open the default Apothecary interface and Motion at the same time. You can use Motion to set the Container and the main ingredient, and to see what ingredients and additives you have at a glance. Motion sometimes works fine with additives, but you can add them to the default ui manually if it acts weird. Don't use the Craft button in Motion! This makes it so I can't craft another potion until I relog, and also crafts as many potions as possible no matter what the options are set to. Just use the default UI craft button.
Sart's Apothecary screws up all the time though and he's not even using an addon for it, so your results may vary.