Tonight one of my guildmates, blood elf 67 hunter Lexxia, asked me if I felt like trying out gorilla tanking so he could pick up some achievements. I dithered, then accepted; we were joined by guildmate Amedina, tauren 70 resto druid who's just recently finished her epic flight form quest chain, who's one of my all-time favorite healers to group with.
We rocked the house. Three bosses down, no fuss, no muss.
Now, Sagarmatha is no rival at all for any really competent tank. But I've grouped with plenty of tanks who were something else. And I do now think that Sagarmatha could do an entirely serviceable job as tank in a full group for an instance at our level. I hope I get to try it soon.