Most of the comments above have been in reference to rejueve blanketing / old cata playstyles (even though rejuve blanketing wasn't viable in cata, but oh well...). So I thought I would chime in on ways he could improve his mana efficiency and also so you can check if he is doing them I guess.
1. Rejuvenation overhealing does seem relatively high compared to the majority of other logs I have checked, granted they were top 50 druids, but their overhealing done was around 15-20% rather than 36% on your longest try.
2. His problems with mana do not necesarily stem from rejueve spamming in night phase, perhaps he is trying too hard to heal tsulong when he does not have the bathed in light buff, generally using rejuves / HT / Regrowth without the buff is too much mana to waste. He should wait for the buff before healing the boss while keeping lifebloom up. Also another option for him to look into is specing for Soul of the forest, which is particularly effective on this fight and I have found it to be > Incarnation both throughput and mana conservation wise. Basically as he receives bathed in light, he casts regrowth > Swiftmend > Rejuve > Regrowth , giving him buffed regrowth hot, buffed lifebloom, buffed rejuve with 50% extra haste and the final buffed growth, and letting the lifebloom tick to full duration and bloom without overwriting. This would possibly lower lifebloom uptime, but give a massive bonus to his overall healing. Also SoTF gives buffed WG's throughout the fight which is a massive bonus in night phase.
3. Lifebloom up-time is far too low, even with soul of the forest it should realistically be 95%+ and that's accounting for possible fears etc (which he can avoid by moving 30 yard from the adds, 30 yard range on fear, 60 yard range on sun breath)
4. Someone above mentioned using tranquility during a buffed sun breath phase, in my opinion it's just not worth it. He should use tranqs in the Night phase to limit the amount of rejuve's he is outputting and generally have an easier time healing.
5. He missed 1-2 Sun breaths per fight. Again possibly because of fears, but they are avoidable.
6. Finally his swiftmend usage is to low for the length of the fight (will be particularly important to use if he decides to take SoTF)
Hope this helped a bit