This weak aura makes use of the 'Set maximum progress' function to cap the bars at 3 seconds. This means that they deplete at exactly the same speed, so the shortest bar is the first to come of cooldown. The castbar displays current cast or global cooldown, again at 3s for a full bar, so you can see at a glance which abilities will be off cooldown when your current cast/gcd ends.
The Stormkeeper and Chain Harvest bars only display when their CD is <4 seconds to prevent clutter. The Flame Shock text colour shows whether you can reapply it on your current target, turning green when it's absent on less than 6s left.
It may take a little getting used to, but I found my DPS significantly improved since making this WA, as you can very easily see which highest priority ability is off cooldown when your current cast/gcd ends.
Inspired by the old Event Horizon addon that did pretty much the same thing.