TFD is definately NOT BiS. The on use gives 350 mp5 and the replenish from the int is 26.5 mp5. The mp5 from JoAR is 531.02 and the "mp5" from shard of woe is 405+.
While TFD is very good on short fights where the mp5 from JoAR doesn't have time to overtake the initial mana from TFD. Jar beats TFD on most raid encounters.
I fixed the math on FoM(heroic). Assuming it procs after a 45icd its about 480mp5. The issue i've been having with this trinket is that the ICD is either not 45s or it has a terrible proc rate. With the normal mode FoM I had 4x procs over an 8min encounter, while a few others got 5 procs on the same fight.
Assuming 1.5min proc rate, 207mp5 + 30 for replen. This places FoM under JoAR, TFD, and Core of Ripeness.
The top 3 trinkets would be
#1
Shard of Woe
#2
Jar of Ancient Remedies
#3
Core of Ripeness
Core of Ripeness depends on the comp basically. Mana tides make this trinket amazing since you can easily time this with tide, where trinkets that proc are not guaranteed to go with tide unless tide is saved specifically for you.