I really feel this bonus was added while the test divine favour was active, things are designed a while before we see them so I really think that this was designed one day while divine favour was in it's more usefull form.
A mistake has been made in my opinion.
There are two things that really need to be addressed for this to be a viable 4 set bonus. Firstly please bring back the intended divine favour this was designed for. Secondly please look at how long raid fights actually last, the maximum named fights I am seeing at the moment are arround 8 mins, please let the recast reducer reflect this more somewhat and base the recast on it giving you an extra save per mob rather than how it stands which is you get to use the spell once per raid named. A 30 second reducer makes no difference per encounter and that is the most important factor here so looking at it from that angle it is pointless. The only way there would be a reason for a recast reducer is to allow it to save twice per raid mob which leads to a reducer of arround 1:30 to 2min. (Remember it is a 5 min recast spell)
Its like the recast reducer on the Paladin chest peices for our big heal. I can't understand it as on a per encounter basis this makes no sence appart from a very small minoririty of raid encounters that last longer.
Personally I would really like to see something more in line with what Paladins do to help them stay alive with these set bonuses. I really would like to see the 2 set improve the ward prayer in some way. And I would like to see the 4 set improve the single and group heals we get in some way, I did suggest in another thread that the 4 set add a ward to the two heals I mention, for example a 30% of heal value ward added to each heal as the 4 set bonus. I still see heal interrupts a problem to be honest in raid encounters, by the time you get a heal off somtimes you have lost the benifit of them as your healers (who are not getting hit) have you at 100%. A ward on the heal at least allows some wiggle room for the whole mob hitting you vs interupts vs it being benificial to cast a heal.
Regards
Kahling