There are a couple of options for threat tracking, Threat Classic 2 is JUST a threat tracker, Details! includes other meters that may be useful to you. Pick one or both, up to you.
Deadly Boss Mods and Bigwigs Boss Mods are the two big names when it comes to telling you what is about to happen in a raid or group encounter, either is fine, just have one of them.
GTFO lets you know when you are standing in something that is going to cause the healers extra stress, be kind to them and move out of the stuff that is killing you.
Exorsus Raid Tools has a lot of handy features that make leading a raid easier, please help the raid leaders out and install it.
For coordinating paladin blessings we use Pally Power.
For checking attunement and coordinating finishing attunements, we use Attune.