Patch 4.0.6 (8-Feb-2011): Rejuvenation is now trained at level 3, down from level 8. In addition, its mana cost is now 20% of base mana.
Patch 3.3.0 (08-Dec-2009): The base duration on all ranks of this spell is now 15 seconds. Previously ranks 1-14 had a 12 second duration. Druids will no longer get a more powerful spell error message when attempting to overwrite a Rejuvenation they cast.
Patch 3.2.2 (2009-09-22): The coefficient is 0.376 for both ranks, and in fact all ranks. (Source)