I'll add a classic link to this:
https://web.archive.org/web/20010711...of+Argli&type=
Everlore (in 2001) shows it as 560 damage. If the 2 minute length is correct, then this would work out to the 28 per/tick.
An interesting note, Everlore shows it as Alteration and a 2 second cast time. I'm not sure what to make of the cast time, but the Alteration is probably just a typo (one of the comments mentions it's Evocation).
Edit: It was tough to find classic info on this on Alla since they seem to have changed the page around 2003. Perhaps when they changed it's overwriting with Torment of Scio they also did some other things to the spell (like change the cast time)?