No NPC Cleric has 18 Wisdom, only the values of 10, 12, 15, and 16. So let's start by saying that:
With 10 of Wisdom what does a clerk fail to have? And with 16 the difference is too big? I do not know the answer, if you can explain thank you, because it is something that should be considered at the time of voting.
Constitution and Dexterity (Life and Armor) are as far as I know the next two important statuses for clerics (Po'rme viconia has low Con, but earns a lot of life per level, I do not understand why).
Multiclass with Mage, Thief or Fighter should give some differential, if they can even vote to explain, because for me Clerigo, Mage would be one of the TOPs (Aerie? ^^), but 10 of Wisdom, seems very low!