I really think the Zek brothers are the hardest mobs in Time. Quarm seems a wuss in comparison.
The Emp. Ssra encounter was the toughest for that expansion, due to the complexity of off tanking, mezzing, etc, etc, and the need to have bane weapons and keys. WS pulling him was a real pucker time. VT mobs just had HP, and the zone was unforgiving of any little mistake. There were times you couldn't even use mounts, as they seemed to cause aggro. NToV was a bigger thrill.