Lets be clear once more: Even Shiva Savage dont melt the tank with the speed the OP discribes. Conclusion: he isnt telling the truth or he was undergeared - nothing else is possible.
On a broader picture - roulette is in the past weeks very "swingy", hit or miss - i have tanks that outperform dps and perfect handling of mobs or i get someone that dont even hold aggro, dont do any dps and spinns like a fidget spinner on illegal substances.. and i get blamed at the end, because healer=bad and should be ashamed.