I think sartharion 3 drakes will be near impossible or at least very very hard for a boxer of more then 5 characters, simply because even if you have all dps and healers on follow, you would constantly get the void circles on top of your party. Maybe some day when we far outgear (or outlevel) the instance. :P

But then again, it's a fight most guilds won't be able to do. It's a prestige encounter.

But take 10-boxing with one drake up (shadron if you got a DK tank) will be doable imo. The problem I see arising with multiple drakes up is that you're running from the void zones too much to be able to deliver the dps required for anything more then one drake up. Only one drake up will allow you a lot more time though. Having druid and priests as healers would help too here. If you 10-box solely with holydins, you can probably forget it. Need instant healing and hots to heal-box sartharion with drakes up (due to the amount of movement required).