I have something like 10-12 points in calm and some rings I equip sometimes. I use calm very often, and I am able to keep aggro off of dps during bosses. A lvl 130-145 ranger or rogue picks up aggro fairly quickly and I can calm them to get it back on a lower lvl tank, like lvl 120 or so. Sometimes we have 2 high lvl tanks so we buff up one and want him to take hits, but the other high lvl tank steals aggro. In this case, it's easier to calm the aggro stealing tank and get it back on the buffed one than it is to recast all your buffs on the aggro stealer.
Also, when lvling with a partner I sometimes calm them and take hits myself to help my skill evasion abilities. And I have had higher lvl Druid clanmates struggle with mobs attacking them during bosses and their lvl 1 calm does not remove their aggro because they heal a frickin ton. So I hit them with my high lvl calm and the mob jumps off of them right away.
Back in the days when clans on Danu would always is bosses from each other, I would use a high lvl calm on the other clan's tank. It caused bosses to kill their dps members and negated the damage advantage they might have had from cloak of fire. For those on servers who still have clan wars, it's a fun trick.
In a way, I miss those days, and thanks for doing that to us
