Watch your pet CDs. It is advisable to make sure you have Enkindle, Spur, and Rouse up while aoeing the snakes (as your video mentioned), but that phase is also 6:30 into the fight. You can use the Rouse + Spur + Enkindle combo during the first phase, use Rouse and Spur a few times in between, and still have the CD's up for aoeing the snakes.
While the video points out how you should save enough aether to bane + fester the fast conflags you need to be cognizant of your CD timers. If you're sitting on your aetherflow CD for 30 seconds you've waited too long. The stacks could have been used on festers, and been replenished in time to bane/fester the fast conflag.
For conflags, unless your raid dps is really low, you can command your pet to use its small aoe CD. It'll do slightly less damage to the conflag, but also hit twin resulting in more overall dps.
As with most fights, for phase transitions or movement due to mechanics you can (and should) be casting ruin II on the run. Not casting during these moments is a loss of dps which could be crucial depending on where your raid is at on the encounter.