I'd generally consider 1AP/1XP to be the reasonable lower bound, especially since this is the rate of XP gained from a skill like
Infuse. The only time you get worse is if you are intentionally doing something that you know is a bad AP/XP ratio (Lockpicking) or if you are crafting useful items for the future, such as potion-making.
That's not to say that 5XP for Anoint isn't worth it. After all, it does involve making or finding a potion to use for those XP, so it isn't exactly "free" to use and is worth giving it a bit better XP rate.
A Quick Brown Fox [
id 3412] upcoming ̶W̶o̶l̶f̶ Fox Revenant
ÆĐR [
id 105796] upcoming Lightspeaker
Elly Mentalist [
id 14108] upcoming Holy Champion
erikune [
id 3374] Citrus Tree Planting Wyrm Master
GIANT ENEMY CRAB [
id 109884] Infernal CRAB Behemoth
Osteokinesis [
id 110670] upcoming Lich
Scribalist [
id 3375] Professional Transcriber
Set o Lockpicks [
id 7505] Professional Lockpicker