Inspired from your video i take a look last night into Maghteridon's Lair..

After the trash, at the first try i had a bad position for my tank and got a wipe
the second try was perfect and got the achievement too :P

i switched the Arcane Mage to Frost Mage for the replenishment
at 30% popped hero and everything was smooth as butter..

Here the video but - i have to say - is really close to the supernova's ones...
The trick - imho - is to kill asap the channeler for avoid too much elemental pop out.

Ronin Team
Palatank
2 Elemental Shaman
Arcane (or Frost :P) Mage
Disc Priest

Enjoy in HD
http://www.youtube.com/watch?v=1F4X1j2A6ek