My guild does just fine in ICC-10 with tanks that are 37-40k unbuffed. ICC-10 should be entirely doable for your guy as an offtank, they should let you in to offtank and have their "main" offtank go dps for the night. You will get frost emblems faster, rep towards the ring, and maybe a few iLvl 251 drops.

45k unbuffed as a minimum requirement to tank ICC-10 seems a bit (not much, but a bit) on the high side for me...