We just killed hydross in SSC and are thinkin of going for fathom lord next. Our raid leader however has been bringing up the question as to why we don't just kill the boss directly and ignore or heal through the adds? He wants to know why do we need to kill the adds which give the boss more abilities and then kill him?
Now that this has been brought up, it also got me interested and curious. Any help on this would be appreciated.
A couple of reasons. The first is healing load - with the additional melee damage each tank is taking, you're going to be burning a lot more mana keeping everyone alive. The second is DPS - you have to keep interrupters on Caribdis, DPS killing Spitfire Totems, etc, instead of focusing on the boss. When you've got the entire raid on him, they're incidental. When it's a couple of people doing each job, you'll probably have a lot more trouble keeping up.
When Karathress hits 60% or so he gets a large buff if any of the adds is still alive (and an even bigger one if multiple adds are up). Not much else to say.