Darren i have 2 Wirehaired vizsla's, a 7 year old dog and a bitch who is coming up to 3 ( who is the spitting image of the dog in your picture)
The dog has always been very steady, the bitch runs a bit 'hotter' but her nose and movement are perfect but she is taking longer to mature than him, i did know before getting this breed that they can take longer to mature than most breeds and i would say this is the problem you have.
Stick with it and you will have a great working dog.
If all goes to plan i will have a litter from my pair next year and can expand my picking up team
ATB And