Bear tanks were ideal for ZG and some MC bosses, but would later take too much damage, so people just didn't care about them anymore and decided to not take them anymore as they'd rather just gear up more Warriors. I actually have a Vanilla manual in the Battle Chest I bought for a second account that says outright that Warriors are the best tanks, got a good laugh out of it reading it not too long ago. I also think it said Priests were the best healers.