The Sun Raider Phaerix battle uses the Rod of the Sun (which is buffed to a 3/8 in heroic) to grant immunity to the player that has it on their side of the board. This can be played around by the utilization of Silence and Crazed Alchemist. Holy Champion can get quite large with all the potential healing you can do versus this boss.
Here’s the Twitch VOD of him defeating Heroic Sun Raider Phaerix.
This is a great deck for The Sun Raider Phaerix battle: Heroic. missing 1 Blademaster and 1 Madness. I replaced them with an extra inner fire and shadow ward: death. The shadow ward proved to be a stale card in my hand. I easily won on the second attempt as i able to keep deathlord buffed/healed.