Even with level 1 you can bless one teammate per round. Level 2 in theory grants you the chance to bless more than 1 party member. However, I haven't seen a report where someone has level 2 and blesses 2 or more partymembers. Perhaps this is because most players prefer level 3, which automatically gives +1 to everyone's skills in round 1.
On a different, yet relevant note, I would like to know if an old bug was fixed: If the enemy has Curse of Darkness 3 and casts it on you, your level of Divine Bliss falls from 3 to 2. And there is an imbalance- the enemy decreases the skills of both you and your mercs with 1. But then you raise only your skills with 1.