Obliterate Crits

I feel like my obliterate Crits aren't doing enough damage. With the obliterate glyph, unholy presence, and no buffs, I usually get Crits that do 35k to 50k damage. I just want to know if this is normal or below average for someone with my gear.

EDIT: Oh, and both diseases are up.
Sounds reasonable to me.

Also, swap your runes. Razorice MH, FC OH.
Just checked my recount for my last LFR for Yorsahj, since Hagara's overload would screw with it.

98 obliterate - 48 crits, avg. 27096, max 35300
98 obliterate offhand - 46 crits, avg. 17025, max 22881

I attribute it to the change from frost to unholy presence - The DPS is higher, but the damage per hit is down 15%.
well with my gear i average about 40k obliterates and around 32-35k frost strikes and that is self buffed, so you're fine