I have been playing a life cleric up to level 10 and when I cast bless the players keep the rolling simple by not using the extra 1d4 unless they just miss an attack or saving throw. What I have noticed from doing it this way is that the extra d4 is hardly ever used and in many fights its benefit has been questionable to zero. Often the extra dice is not needed at all and I have wasted a slot and a round. Other times the player misses, rolls the extra 1d4 and still misses. Other times my cleric loses concentration by being hit or wanting to cast something else (encounter changing) like hold person. And occasionally the spell turns a miss into a hit. In fact the spell has so little effect on the combat it seems that the other players often forget its running and I have to remind them.
I would say its an ok spell in general but hardly an encounter changer unlike a timely healing word, hold person or dismissal. But then its only a first level spell so I guess that's fine