I have not personally needed to use one, generally though I hold holistic medicine in pretty high regard. In your shoes I would absolutely seek the opinion of one! Especially since the current treatment isn't working. Traditional vets tend to just have a sort of "one size fits all" answer for things. Like with food issues, I don't think a "hypoallergenic" diet is the answer for everyone... is it impossible for a dog to do poorly on it?? Probably not, but this is what every vet jumps to and if the dog doesn't respond well, then I guess the next option is lifelong prednisone.
Holistic vets look at YOUR particular dog and take in the whole picture, and can create a more tailored treatment. They tend to be more... creative.
My friend has been seeing a couple holistic vets for her 8 year old dog, for the past 2 years. He's a cocker spaniel, and if you know anything about cockers you know they are basically just one big ball of allergies. His entire life he has battled chronic ear and skin infections. Constantly on antibiotics and yet still never really doing well. Right now he's doing the best he has his entire life, NO sign of infection present, by being put on a raw diet and on a combination of herbs picked specifically for his problems. It took a while for them to get to this point, but he's made more progress in the past 2 years than he had in the 6 years prior.
I try to treat as holistically as possible, but in a DIY way just by reading the internet. My cat has IBD and I've managed to manage him beautifully on my own (if I may pat myself on the back

) just through regular OTC diets. He occasionally has a flare-up, but I would expect this with all IBD animals. Whenever this happens, my vet tries to convince me to put him on a hydrolyzed protein diet + pred. That always just sounds drastic to me, there are so many other options worth trying first IMO! Usually all I have to do is rotate him to another "safe" brand of food, and he's back on track. Easy.
If Boston indeed has some sort of allergy/intolerance, my experience is that traditional medicine approaches it horribly and the pets never do WELL on their treatment. I work at a vet clinic. The vast majority of the animals I see every day have some sort of allergy, to some extent. Most of them do "okay" or are "pretty under control" (the words of their owners), but still exhibit symptoms and/or require daily meds forever. They may be better than when they started, so the owners are content, but the issue is still present. We just had a dog come in today, with a history of chronic loose stools. He's now on a hypoallergenic diet + prednisone. His loose stools are now just "off and on." The owners consider this doing well.
SORRY I did not mean to turn this into my ranting soapbox but it is one thing that upsets me soooo much about my job, because I know there are options and other ways that can work better!
The short answer:
I would not hesitate to use a holistic vet. :p