I tend to get quite defensive.
The number of times I've read "these will be good enough..." when referring to brass bands whilst talking about mics I wouldn't even use for holding doors open....
Having a good transient response doesn't necessarily mean harsh and / or brittle.
WRT to Soundfield recordings of brass bands I've also encountered quite a few individuals and companies who try and sell them as the be all and end all to recordings such as these. I'm afraid - IMO at least - they're not.
In terms of post processing it all depends on what you need to do. I've a tendency to leave things well alone if I've got it right at source, but as I've said before you
will run into venue problems with most bands or you'll be dealing with people who are inexperienced at recording and / or are young or inexperienced in which case you may have to fiddle.
They're not as easy to record as a lot of people try to make out....I wish you luck with it....although not too much of course