from my experience and opinion if you go for krivis, make it C2 or 3 or else give it up, at C2 you will get attribute that make zaibas an aoe and It will surely help much, My healer is at 200 currently with krivis1 and I’ve found that only zaibas of krivis1 is quite poor at high level. Krivis1 is not so bad, you’ll get daino and zalcia which is surely good but to think losing 1 circle for these, maybe we have a better choice.
For Chaplain. the reason why people go for Chaplain after priest3 is that the chaplain is like a priest4. It’s skills amplify priest’s skills. And I’d say if you have priest3, chaplain will be far better than an oracle for you.
For plague doctor build. Wurstbar has given a best reason why his build is among the best choice , and I can’t deny him
Myself, just start a new character aiming for Cleric> priest3>chaplain and will decide for r6and7 later, if possible will be oracle>kabbalist or if I find cleric1 is not enough for healing, will go for cleric2>PD (if no oracle,I need PD’s blood letting for debuff prevention)