He has a frontal AE that does slashing and divine damage.
He casts a blue bubble that you need to be inside of before it bursts, you have maybe 3 seconds to get in there. When bubble bursts those on the outside get hit pretty hard and are knocked back. Interrupting him did not appear to stop him from casting this.
Don't AE the fans.
At 75%,50% and 25% health Drago will FD the entire group (zonewide) and run to the crowds cheering, this gives him a beneficial buff. The FD is scripted and cannot be stopped by interrupts/stuns etc... He will also FD the group and run to the crowd if ANYTHING dies during the fight (pets, dumbfire pets etc..) He will run to the crowd on one side, then the crowd on the other side and then you will be able to stand. He will usually cast his 'blue bubble' just after cheering to the second crowd. Be sure to run to the bubble then pull him back to the centre to avoid aoe's hitting the crowd.
The fans can be killed, but re-spawn quickly so there isn't much point in it.
He will leash if you run out of the door.
Bug: Sometimes you will end up perma FDd on the floor - you can move around as corpses, but you can't cast on Drago. Evac'ing won't fix this, but having everyone zone out and back in will.
Spamming /cheer and /flex during the fight can steal Drago's buffs and give them to your own group. (*Edit: You can gain the same buffs that Drago gets by sending someone in your group to /cheer and /flex at the crowd. That person(s) has to be standing on the platfrom in front of each crowd, but still needs to run inside the bubble when Drago casts it to avoid the additional damage/knockback. The buffs last for approximately 30 seconds, and will affect all members in the group. The buffs give substantial increases to stats and crits, and while it would be possible for high-end players with great gear to kill him without the buffs, the buffs make it much easier to succeed on this encounter.)
Once Drago is dead, and if you're feeling particularly brave and unstoppable, stand on the platform, target the crowd and do /rude. (The crowd will attack the player who performed the emote.)