The suggestion for 3 levels of cleric was to get access to a better cure spell. With empower healing and some heal amp it should hit for around 70 points. Which is not to bad seeing as a cure serious pot will only get to around 30. With 3 levels of cleric that will be around 180 sp (with a 8 wisdom which will require a pot to be able to cast), which will get him around 10 casts (of empowered heal cure moderate) between shrines. Turn off the meta magic and the spells cost less than 12 sp each to cast. With echos of power going he can heal as needed til full and going on to the next group of monsters. Cure light is 6 sp and cure moderate is 8 with empower healing that turns into 16 and 18 respectively.
I believe that Clerics have access to Echoes of Power at level one. Casting Cure spells from that is only ever going to be a trickle, so you might not want to bother with more levels. You will also need to get your Wisdom to 11 to cast.
The most important thing that the level of cleric does, is grant access to wands. Not just Cure Critical Wounds, but other spells such as the Remove Curse/Disease/Blindness and defensive buffs.