For Zon'ozz I can see Sub being ahead if you have to kill a lot of eyes and the claw would be dead till you arrive on the boss. But usually I'd have to kill an eye or two until the boss moves to the claw position and then get back on him and cleave hard.
Well, yes, Hagara. It's as I mentioned. You will do more personal DPS with Sub but the cleave damage on tombs should in all cases result in more raid damage on the boss. I only have a
10m parse right now (since we're rebuilding the FtH 25m raid) in which I did 1,2m damage via Blade Flurry. If I was Sub the other players would have to deal these extra 1,2m damage on the tombs resulting in longer tombs and therefore lower Boss DPS uptimes for the players outside and especially inside of the tombs.
For Blackhorn I guess I should let you play it on heroic first then. However, the issue you mentioned with adds moving too much might be caused by your tanks. I sadly haven't seen Warmaster on your stream yet.
Here's an example though. In the
first phase I dealt about 23% with Blade Flurry which only gets better in the
second phase. Sadly I can't link a full attempt as I switched onto a shadow priest for the kill but it should give you the right idea. Also, again only 10m.