The Czar of Sporeggar

"World of Sporecraft"
Would have been a much better acheivement name.

I just did this on my Paladin via Sanguine Hibiscus turn-ins. Normal UB is very easy and fairly quick. I averaged 30-40 hibiscus per run, which took roughly 20-25 minutes. In all, it took me a little over 1.5 hours and 4.5 runs to get the 165 hibiscus I still needed for exalted.

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Walkthrough:

Basically, I went Ret and cleared every mob up to the first boss. Keep Sacred Shield up, use Seal of Blood with Judgement of Light, and hit Divine Plea every cooldown. If you have 4-piece T7, it really helps keep your mana up. You should be able to grind through without stopping to drink. I killed the first boss since he can drop a hibiscus, then cleared all of the giants and bats after him. You can skip all of the nagas except for the first four after the first boss (the pat on the bridge and the guardians). When you get to the hydra boss, stand on the ramp and pull him with Hand of Reckoning, then just nuke him down from there and swim across the fish-free water.

Here, you can skip all of the trash, again. Just be wary of the pats as you weave around to pick the few hibiscus along this stretch. Kill the hunter boss and collect the hibiscus on the ground, there, then kill the couple of giants remaining. Be sure to look to the ledge on the left before you turn right to kill the Black Stalker, as there's usually a plant out on the edge. Kill the stalker, collect the plant in his room, then hop back down to the entrance.

If you want, you can walk all around the area leading up to the first boss to check for any plants that may have spawned after your first pass. I usually picked up another 5+ this way.

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Opportunity cost:

On my server, hibiscus sell for roughly 5g each. 165 looted would net around 825g, which took roughly an hour and a half to farm, totaling 550g per hour. This is more than I can earn through herbing Icethorn and Lichbloom, which come at a rate of 7-8 stacks per hour sell for 40-45g per stack (280-360g per hour).

I'm not sure how it compares to mining and prospecting, since I haven't really done much since the 3.08, but I seem to remember getting 400-500g per hour farming cobalt at 40g per stack and 500-600g per hour prospecting saronite pre-3.08. Prices have plummeted since then with the increased speed in mining and gems being available through badges, so I'm sure the amount earned per hour has dropped by a couple hundred gold.

The point is, it's definitely worth it to farm Sanguine Hibiscus rather than farm something else to buy them off the AH. However, they're typically not worth farming and selling as they don't sell as fast as herbs or ore (much less demand).

Sorry for the massive wall of text, but I felt that I should share my experience in great detail as an alternative to killing naga :)

Czar, Tsar - supreme ruller in some countries Tzar