Good topic @Yenneavi and I'll defiantly will check those out. I'll have a few other recommendations I can add as well.
Especially if you're DPS'ing, Rift Meter is pretty essential. After playing with this for a while I can't even imagine playing without it anymore. It can show all kinds of useful stats but I mostly use it for the DPS dick swinging contest and to make sure nobody is secretly off-healing (j/k). It's not only useful during combat to make sure you're pulling your weight but also when you want to tweak your build (to make sure you're actually tweaking it for better and not worse).
King Boss Mods
As I mentioned in my other post, KBM is pretty much a must-have for people running SLE or above dungeons and/or raids. It's pretty cool on CPU usage too so most people should be able to run it. It shows upcoming boss abilities, bigger and more clear cast bars and helpfully flashes the border of your screen when you need to be aware of stuff. It does some other stuff as well such as showing boss phases and timing the fights. Highly recommended.
I use Imhotar's Bags to keep track of items between my different toons and stuff in the guild bank. I don't use the actual bag interface itself that much but I like having the quantity of a particular item on my alts, banks, guild bank show up in the tooltip. So when I'm on Aazeen I can see that Nanira has like 20 attainium crystal for example. It's a little bit of a CPU drain so run this occasionally when I'm not doing anything special.
The Resource Tracker is a bit of a resource hog but I usually turn it on during questing/foraging anyway. It keeps track of resources on the map and shows helpful arrows helping to find the resource. It's not really essential but sometimes when I'm foraging I see like 3, 4 resources and after picking up two the other ones have scrolled off the map and I forgot where they were. Also it's useful to filter out particular resources that you can't or don't want to pickup.
KaruulAlert is useful to manage and juggle your buffs and cooldowns. To be honest I'm still figuring this one out and I don't use it that often. Also I'm not too big of a fan of the interface, it's a bit weird and also this thing has a lot of options so it might take some time to master. I've heard good things about it though and after trying it out with my pyromancer I can see the use. Just have to learn how to work it better.