Originally Posted by
quitefrankly
You should be using weapon chain
It depends on the situation. You use the CD that you think will provide just enough defense to overcome your opponent's offensive cooldown, but no more. For example, you probably don't want to use both Touch of Karma and Fort Brew at the same time, since Brew Karma alone should provide enough defensive to survive any kind of burst.
In general, you want to avoid overlapping defensive cooldowns, and overlapping defensive cooldowns with your healer.