Aggressive Horn is the ultimate on your front bar. Did that sound like a suggestion? Because it wasn’t.
No but seriously, it’s absolutely vital for a raid team because it increases hp/mag/stam 10% for 30 seconds for your group. This means they’re sturdier and can do more damage. Keep in mind the Minor Force buff times out at 9.5 seconds, so blow the next horn at any point between 10-29 seconds so the attribute buff doesn’t fall off. Remember your ability to heal will be judged based on your uptime for this skill, so prioritize it. It takes some time to get used to coordinating it, but with practice you’ll get it. Try any or all the buff tracking add-ons so you don’t have to count it down in your head: Srendarr, Untaunted, and BuffTimers are popular. Also remember to communicate with your group so you don’t “double horn.” Tanks have priority because they may need the resources, so let them blow it if they call it.
Assuming you do nothing else that generates ult, one LA will result in 32 added ult every 9 seconds, which means you should be able to get your horn (at a cost of 240) up every 67 seconds at minimum. Tanks wear sets that bring the time down more, some to as little as 45 seconds. Except in rare situations, both healers and both tanks in every trial will run it and there is no reason for it not to have a 100% uptime between 3-4 support, even on trash.
Thank you to Harven for a wonderful little add-on that lets you see different morphs of a skill. Super handy!