I play Disc in 10 man guild, and my secondary specc is Holy, but i only used it on Tsulong so far in contrast to Dragon soul where i offten swithed my specc between bosses. We manage to kill first 5 bosses in TOT and i didn't saw fight witch favored Holy. Is there any boss in TOT where Holy specc is absolutely mandatory? If not, i think having a dps off spec would be far more useful then 2nd healing specc witch i hardly use.

What about you guys? What is your 2nd specc?