Thus far, overall boss difficulty consensus (at least on 10man):

Flame Leviathan - easy, hard mode (at least one orbital defense left up) is considerably more difficult.

Razorscale - easy, only takes a few tries to get the hang of.

Deconstructor - fairly easy, adds can be a problem and he had a harsh dps cap.

Ignis - "difficult" until you grasp the concept.  Brutal on healers but otherwise straightforward, long fight.

Kologarn - joke on 10man.

Iron Council - fairly basic multi-boss fight, only thing that makes it difficult is positioning and the death runes.

Auriaya - can be kind of harsh, particularly w/o a shaman or priests, but otherwise fairly straightforward.

Hodir - easy on 10man, only takes a few tries to get the hang of.

Thorim - pretty easy, room is large enough to make spreading out and avoiding linking chain lightning a problem.  Just learn your necessary group comps (hallway and arena groups) and it's simple.

Freya - remarkably easy, we one-shot her on our first night of attempts, ever.

Mimiron - DIFFICULT.  Takes a lot of adjusting and learning to avoid everything that is going on, lots of ways to die and screw it up.

Vezax - moderately difficult, requires a lot of control and learning what the "Mark of the Faceless" actually does.

Yogg-Saron - very difficult.

And by reimburse you for your time you mean....oral?