Splatterfart is right- there is no easy, 100% of the time answer here.
Much depends on the quest being done. If there aren't many shrines, then I really don't want to see the healer(s) using their sp buffing IF there is another character in the group that can handle those necessary and/or helpful buffs. The same goes for a Wizard; if the Bard can handle Blur, Rage, Haste, etc., then I'd want the Wizzie (or Sorc) keeping his spell points for damage output.
This is, of course, assuming that there is an alternative (in that example, a Bard). If that isn't the case, I prefer seeing the Sorceror or Favored Soul handling the buffs because they have more spell points. If we have two Wizzies or two Clerics, I prefer having the one with the least sp buff so the one with the higher hp can max damage output or healing.
One thing I have discovered in most PuGs is that I should expect no buffs at all and be pleasantly surprised when I receive them without asking. If I am a buffing class, I pass out the 'basics' (Blur, Rage, Haste, Resists) without waiting to be asked and provide things like Jump upon request.