I'm just curious about why cleric healing I and II was chosen for requirements.

This is more a herbalism enhancement since it affects the healing skills you have and how you use them when somebody rests, (or if you ever use a healing kit)


Since radiant servant also increases your LIGHT damage spells..

I'd say Cleric Smiting I and II OR cleric prayer of smiting OR cleric energy of the zealot II would be more appropriate.