I'll definitely try that next siege.
Wasn't able to do it, the speed was too much of an issue even with all that setup. Taras was built too tough. Taras had dec def, my Rotos with 7k Atk and 300% crit dmg did his A3 against him and Taras took less than 10% of his hp in dmg.
A Cardinal-based team did almost work, but Siphi put her to sleep before she could rez.
Was "High Elves Only" an option for you this time? If you run the Islin team, good luck.