On heroic the first 3 bosses are laughably easy, all 1 shots.
Goroth is the same as he is on normal you just rotate him 180 degrees if one side fills with flame
Demonic inq is just a tank and spank, we used 3 tanks but i dont think its required, we used the whirlwind as the tank swap mechanic
Harjatan was just a quick rotate at 100 energy and move out of puddles
then the fights start getting a little more difficult
Mistress took us about 5 wipes mainly due to Hydra shot and people not knowing where to soak. the fight gets very cluttered very fast especially in phase2. if the tank with burden of pain gets hit with a hydra shot its GG as it takes about 75% of the raids total health away. the little eels do shadow damage so off tanking them isn't an issue. this fight is going to be a pain on Mythic.
Sisters is pretty awesome, This fight can be solo tanked as the only tank swap mechanic on heroic is the moonglaive and if youre fast you can drop the debuff from it by crossing the Lunar Boundary. we had 2-3 wipes once again from soaking, there is a lot of "stand in this straight line" mechanics in Tomb. healers here definitely have to plan their healing cooldowns around bursting the shields on people or it will easily wipe the raid. this fight on mythic is going to be rough, as every time someone crosses the lunar boundary it does raid wide damage and you cant simply just run back and forth constantly.
desolate host - this fight is very complicated and is hard to explain to people concisely, we had people asking after 2 wipes wtf do i do? basically you split the raid into 2 halves you have half up and half down. the half up have to deal with the desolate host (the big cage on the wall) and the half down have to deal with the shadow priestess that both share HP. people up and down cannot see each other, but if they come within 8 yards they pulse for ~1 million damage. the adds that are Up periodically put up bone armor which reduces the damage they take by 95% this is broken by someone down that has the shattering scream debuff stacking on the adds. the issue here is that you cant see the adds on the other side so you have to pre-setup a spot for the down person with the debuff and the up person with the adds to meet (we used the middle of the room). the only other big issues in the fight is everyone that is down with the exception of 2 healers and 1 tank has to leave whenever the dark priestess does "wailing souls" its a minute long channel that pulses damage (very low damage). occasionally during this phase people Up will be teleported Down and they will need to leave the spirit realm by clicking the water bowls. you rinse and repeat until the priestess and the host are at 30% (they share hp). at this point a marrowgar add spawns that has to be tanked immediately. during this phase you need to continue killing the priestess and the giant cage on the wall (they still share hp) and then burn down the marrowgar guy. he rotates through 2 different Aoe's and both have to be soaked, the first is always soaked by people Up and the second is always soaked by people Down. this ability is also the tank swap mechanic for the fight as the aoe does falloff damage.
we ended raid there so we'll get to see Heroic Maiden tonight, when we logged off we were number 20 in the world (lol heroic progression) with 6/9H and 9/9N.
KJ on Normal is a bit boring since the 2 intermission phases where he flies around and does dreadflame really only means you stack in the middle and spread for the circle flames so its really just hanging out and waiting for him to land. i'm sure there will be adds / other bad things on heroic and mythic difficulties. overall i like the raid better than nighthold and i think the encounters (even considering the mythic mechanics) seem a bit more even across the board.