did some testing with Wisdom today. It does NOT increase your 'healing bonus' rating in your score, but DOES still increase your healing ability. It is a fairly minor increase however. I'll share some data below:
controls are level 50 priest, no secondary active, no weapon equipped (0 healing bonus). Using lvl 30 Regenerate (128 hp) faith lvl 40 (25% bonus)
WIS-actual hp per tick
446-167
540-171
548-171
627-174
666-174
725-174
746-178
798-178
848-178
858-178
873-178
882-182
903-182
929-182
929 Wisdom gave 1726-1792 range with level 35 heal spell (still no weapon equipped)
446 wisdom gave 1488-1546 heal range
hope this helps
thank you! data is everything

i've done quite alot research in RoM mathcraft and analysed your data.
i used only
446-167 (called wis0 in the graph)
540-171
627-174
746-178
882-182
becausethe other values seems to be rounded and dont give much additionel information.
as you see in the graph i attached, there is a linear behaviour between normalised change between Wis and Heal. the slope is so close to 0,1 and the rounding mechanism seems to give lower heals in gerneral, that we can expect it to be 0,1.
note that even without a weapon you will have some default Healbonus value!
in words: 10% more Wis = 1% more healbonus from Wiz (need tests with different weapons to know more)
so if you like it would be great if you could do another test with a weapon, also with different spells. (write me a pm if there are updates

)