The statement was based on cleric word: 'bst needed less healing'
You should have slapped your guildmate immediately after he said that.
You cannot, repeat
cannot, derive any conclusions from that statement. The amount of healing you need isnt equal to damage mitigation, its equal to the mobs dps, and depends on
1) your avoidance
2) your mitigation
3) mob being slowed, and what slow%
4) mobs getting stunned part of the time
Here's the thing: #3 and #4 have by far the biggest effect on the mob's dps. When you're gonna do a class comparison, you have to eliminate any variation in 3 and 4, as was done in the parses linked in the replies before me. Once you're looking at pure avoidance and mitigation, monks beat BSTs hands down.
and monk's claim that monks got 200 - 300 ac penalty which bsts doesn't have.
Rubbish. Monks do not get a AC penalty. They used to have a mitigation bonus instead of a penalty, and it was that bonus that was removed. All leather classes mitigate the same, all chain classes mitigate the same, and all plate classes except warriors who get a bonus mitigate the same.
/hugs