Templar's Will

"This supplication will improve the saving throws of the paladin, while making them resistant to poison or disease. This bonus increases with the paladin's level." I can count on one hand the times that it buffed the -# vs Spells. The rest of the time it is random damage reduction for disease or poison. Why is that not 100% of the time per the helpfile? Is there a conflicting supplication that won't let you have the buff?