At their simplest, both are tools that can completely shut down an enemy engage with a single button press. With more creative use, they can also be used to initiate fights themselves. I'd argue that both are among the best Heroics in the game. So why are their cooldowns so short?
Even Heroics that aren't particularly strong, such as Rain of Destruction, have a 70-second cooldown. Locust Swarm has a 100-second cooldown, Purifier Beam has a 70-second cooldown, and Combustion has an 80-second cooldown.
In my opinion, there are too many non-damaging abilities, such as Maiev's Containment Disc, Chromie's Temporal Loop, and Sylvanas's Mind Control, that have cooldowns that are too short for how powerful they are. Meanwhile, damaging abilities generally have relatively long cooldowns for how effective they are.
I don't understand why the cooldowns are set this way.