I havent done, but it would be really hard with only one char. It probably could be done with two accounts simultanously:
- 1 GD tanking scalis
- discord scalis
- one additionally healer
I am not shure, how much healing is needed for the gd to stay alive but I would guess that the mana reg on a discord-tamer is not high enough. So probably a mystic-tamer and a mystic discorder should be able to do the job. (The trick is that scalis spawns the eels on the gd and kills them afterwards with his own ae-spell/damage if no one does ranged damage to him.)