Priest or Druid?

Durance. Admittedly, I haven't played PoE since much earlier versions, but back then, druids were thoroughly underwhelming and Durance is an awesome character.

 

The druid got a major boost since back then - in the current version of the game the shapeshifting form is actually viable throughout the game, with surprisingly high damage output capabilities mid to end-game.
While you will need to build around it, and shapeshifting still lasts a bit too short to my liking - it's been made viable now, so you don't have to stick to spellcasting as a druid.
That said, with hiravias' form being locked in as stelgaer, you don't have as much flexibility with him as you would have with a PC druid.

The priest is still really useful - he can complement pretty much every party, though at the lower levels he is frustrating because you don't really have too much useful spells to cast.
Just recruit both of them and swap them out accordingly - whomever you're not using will sit in cad nua for you and still gain xp (though they'll be lagging a level behind your own if you leave them alone long enough.)
Take along hiravias more during the lower to medium level portions of the game, then at around the halfway point you want to start phasing him out for Durance.

 

I like to take Durance along. At first I didn't care for him at all but after a time I realized he is important to the player character and I am big on actual role playing. Sometimes I may leave him at the Fort but. I try to play with all the characters at least to some extent. Do their quests and certain ones work best in certain situations.

 

Durance has some really interesting conversations with the player throughout the game, as well as a greaty backstory, being involved in the killing of Eothas with the godhammer, and you'll be working on his personal quest well beyond the halfway point of the game.
I kinda wish some of the other characters quests were a bit more involved - both Kana and Eder's personal quests feel like item retrieval quests that don't really go anywhere, and offer the bare minimum i nthe way of character exposition as well.

 

Kana's quest is pretty much a retrieval quest but it lets me leave him at the Keep without guilt. When I role play the characters become very real to me. Eder's quest I think is more a psychological quest because how you respond to him is deceive in what he decides.

i agree about Durance's quest and have come to think it one of the better ones.

 

One thing i'd like to have seen more of is interparty banter a la baldur's gate 2.
Conversations between Eder and Durance could have been pretty interesting, seeing as how Eder is a worshipper of Eothas and his brothers involvement in the war, with Durance being on the other side of the spectrum.