as of now (beta 0.1) you can also find this one or other divine weapons (1h sword, mace, axe, dagger) in a tower near Ernwick (Zombies are around level 25-30 in that area). the spot either has a random divine weapon or nothing (probably if you reload and go there too fast again or just purely random). looks like a white square on the map to the left of the "Ernwick" name tag on the map. it's on the top part of the tower (which is not where the initial staircase ends, there you only find stuff like the perth captains sword)

oh it also includes the laboratory and study quest

I shower everyone how to get the Divine Greatsword in 5 1/2 minutes and level up to level 40 in 12 minutes
search "The Black Masses Super Speed Run" on youtube

I notice a clue to The Divine Greatsword in the book just below the heart in the Heart Tower.
I guessing that you would probably be around level 40 by this time.
I also notice the Zombie bug were they just walk past you also and ignore the night soldiers as well they don't fight one another.

I found that you can just, go right at the start 85HP and just climb over the rocks, run over to Faymoor if you don't die on your way there.
But do not set the knight to attack the zombies as all the zombies in Faymoor will run as soon as you get into the village. You just sneak past the zombies by the cost line.
They won't run like mad after you. Just climb the low wall into the church. Take the sward and then level up to level 32 with the red zombies, level 40 if you take out the red zombies on the left side path to Faymoor as well. I done this so many time find it the easy way to get the sword at the start.

It is quite possible they might make getting this sword harder in the future. Other then that, yeah, quite easy to obtain once you know about it, even if you started a new character.
And about the bug of you being ignored, yeah, same thing, was funny...until it got irritating since the zombies wouldn't group up anymore and just simply scattered.

If you get the greatsword like I did, then go to the drunk captain... I think that breaks the zombie AI... I am walking through zombies and soldiers that wont target anything...

I was lvl 30 by the time I got the greatsword btw.

I got the quest to find the Divine Greatsword after clearing the heart tower(I did that at lvl 28). I ran down faymoor pass and bunny hopped over the swarm in the valley. I used my sergent mace and ground slam once I was surrounded in the swarm and ran over their heads to a walled mini-town. Then I ran across houses roofs and climbed a wall to get into the church. This was kinda easy... But I did cheese the ai a bit.

i made it at lvl 24 i used the solders as a distration and ran into the city then i climbed onto some scafolding to let the possesed calm down then i ran into the church