Exactly. With the 10% nerf Ultra is definately the 2nd (or even 1st) HC boss to go for, and it will just get more clear by every nerf. Yor'sahj isn't affected that much by the nerfs since it's mostly about planning and doing mechanics properly. Atm if you would progress from scrath in 10 man I'd reccomend Morchok -> Ultraxion -> Hagara -> Yor'sahj -> Zon'ozz -> Warmaster -> Spine. If you have good geared people you could probably just go Spine even before Zon'ozz if it's possible, lol.