When you have damage everything becomes easier. We lost a few people 1 month ago and had to replace. We also took the opportunity to BIS everyone in our raid team and then go nightmare. What a difference. We practically one shot TWH with our new group. We got to the dreadguards and on our first 5 pulls we got kelsara down to 50% before we all died. My advice, do not do nightmare if you do not have the gear, it will not cut it.
Some of my raid's damage last night on the TWH.
I have still not found a way to prevent lag spikes when I stream and this shows on watchman as any delay in abilities drops your DPS significantly.