Pursuers Greatsword is... Great, if you like the regular Greatsword (which is an ultra greatsword-class weapon). I think it's a little less durable, and not as good at first, but it gets around 50+ damage per rank and it scales well with strength. I think it scales decently with dex too.
Are they really that good? Specifically right now the pursuers soul....is 8,000 souls a better option than his greatsword or shield?
Depends on your play style but to be honest 8,000 is chump change in terms of souls once you get going take Iron Keep for example. I net in around 40-50,000 wearing Jester Arms and the soul ring up which i forget its name.
The Dragon Rider soul has a sweet bow bit heavy but very useful in terms of power.
So I would use the souls for the weapons to be honest because some of them are epic.
The Pursuer's shield for example I heard makes you float when you jump possibly extending jumps I didnt get it so I dont know how true that is.
I have an answer to everything whether its a good answer is entirely irrelevant