4/5'd HM the other day with one tank in 69's, me in 72's and the other pug dps was probably not in 75's either. While the other 5 in the group were mostly in 75's I feel this op is more balanced towards verpine/augmented arkanian, you probably don't even need min/maxed underworld to pull it off.
I'd agree with you on the first 4 bosses, you could pull it off in 72's no prob maybe even a bit less. However the last boss throws that all out the window. The healing and dps check on the last boss is extremely tight, You can probably pull it off with a really good group in min maxed 72 gear but for most groups that boss will be impossible without fully min maxed 75 gear. I don't think that boss will stay as is but if it does its going to be a huge road block for a lot of teams. That being said I hope they don't change it, it will be a good challenge for a lot of guilds for a little while.