Divination & Math - Is it worth using in dungeons? Only in specific situations?

[Seraphor]

Hmm... and those Lords and Ladies can all go to DPS, whereas the AoE of Divination is diminished on Healer and Tank.

EDIT: I took your maths for granted, but actually you're not adding 6% from Div to 18%, you're adding 24%, because that 6% hits four people. So it's a total of 42%. But 12% of that is diminished, so effectively it's probably more like 36%, and less still with healer downtime.