Our first week in Tomb of Sargeras was particularly fruitful, giving us 8/9H (and 9/9N) with some attempts on Kil'jaeden.
The second week was even better: after doing some heroic on Tuesday, we turned our attention to mythic on Thursday, to see if we could nab our first mythic boss kill of the new tier. 22 attempts and an additional healer later, we downed Goroth. With no enrage, relatively easy mechanics to learn, and a high amount of healing required even with everything going right, it made sense to simply add a healer while we're still undergeared. It worked well, and was instrumental in getting us the kill.
Congratulations to everyone on a well-earned kill! One down, eight to go.