Mists Convergence activating more often since patch?

I noticed that Mists Convergence has been updated to now spawn the Stonehead boss from Siren's Reef, but the other night I was a bit surprised at just how often this instability appeared during that single fractal. At one point it seemed like every few seconds out popped a Mossman or a Champion Rabbit.

Was the "cooldown" of this instability changed in the last patch, or is Onyxia just deep breathing more?

That is correct. It currently activates exactly every 25 seconds, including the time the summoned mist convergence is active. E.g. From the start when Mossman is summoned, and then chases you around for 10 seconds, and after those 10 seconds, another mist convergence will manifest itself in 15 seconds.

I do not quite remember the old interval but it offered a lot more downtime than this.