The "jump" is intended to be a growth of sorts, the spawning of a new rejuv on a new target as a 2% proc each time a rejuv heals someone, without consuming or otherwise impacting the rejuv on the original target. That's about a 12% chance to spawn a new rejuv for every rejuv that you cast, which is close to one free rejuv for every 8-9 that you cast. Since most encounters in ICC have a portion of environmental damage, the rejuv will at least be useful (in most cases) to whoever it does spawn to when raiding in that instance. With revitalize, a bit more so, around the usual overhealing.
- 12% chance to spawn a new rejuv for each rejuv cast, assuming no overwrites of spell ticks
- 1 free rejuv per 8-9 rejuvs cast (again, assuming full ticks)
- Glyphed Rapid Rejuv will spawn new rejuvs faster due to faster ticks
- The spawned rejuv will still likely jump to pets or overwrite/refresh existing rejuvs on their new target.
In 25s, I can see this being somewhat useful, where you are less likely to already have rejuv running on the target it spawns on (otherwise it would overwrite the old, like a refresh), and you aren't likely to be able to pop a rejuv on everyone that you'd like to. However, it still has a chance to just choose someone who already has a rejuv on them, simply refreshing the spell, which in turn reduces the chance that each rejuv you cast will proc a spawn since the previous rejuv won't tick itself out fully. Small fries, but it makes the mess of trying to model this proc!
In tens, keeping rejuvs running on most of the raid is rarely an issue, especially if you have three healers. In two-healer situations where tank-healing is more intense for the druid, especially in cutting edge progression for the group's gear level, the set bonus could be useful, but there is still a much higher chance that the rejuv will spawn on someone that already has one running.
In short, the set bonus is meh for 10s, better for 25s, overall worth getting IF YOU ALREADY HAVE CAPPED HASTE. Due to the amount of crit on the T10 set peices (3/5 pieces are crit rather than haste), I intend to make sure I get haste-capped through gear selection before I get the crit pieces of the T10 set for a 4-pc bonus (given restriction to ten-man raid gear and unreliability of 3% haste aura in my own small raids). If/when I do have to get the crit pieces, I won't be too upset, though, as crit is still very useful with Swiftmend, Nourish, NS+HT, and Regrowth.
I do find it ironic that in order to get the rejuv-chaingunning-raid-healer set bonus, you have to take crit stats that the tank-healer druids prefer. :)