If you want to do Wind and Brass Symphonic/Marching/Jazz bands, HALion has potential but it's not in the most obvious places with currently existing HALion libraries. You get some options in the box with Dorico that are worth exploring but they're not exactly obvious to anyone that hasn't been using HALion over the years.
I can show you a few tricks (but probably not today) to start milking HALion for surprisingly NICE sounds. Knowing where to look, and tapping into the effects are a BIG game changer. Even the slate of GM sounds can be quite convincing (and in my opinion as good or better than Sibelius Sounds 7.x).
Hint: For tutti work take advantage of some the more generic sound Patch Names in the SE Baisc and Pro content packs such as a general "Brass" patch, and keep an eye out for the 'wheel' patches which are going to use the Mod Wheel for dynamic control instead of velocity. Also keep in mind that a touch of the right effects (either in HALion itself, or on the Mixer Insert chain of Dorico) can go a LONG way to shaping up more realistic and pleasing solo brass and wood wind sounds.
When it comes to HALion SE, think it more like a Yamaha MOTIF Rompler (really nice Keyboard Workstations). It's highly capable of producing really nice sounds...it's just important to think of it differently than a 'sampler library'. It's a general purpose 'stage instrument', or 'composer workstation' synth out of the box
I've gotten some great professional and polished sounding results with HALion SE and the Basic SE and Pro SE content packs over the years.
If you're still not getting closer to what you want after getting to know HALion better....until we get more Wind/Brass band kind of 'Sampler Style Libraries' for HALion....
I can recommend Garritan Concert and Marching Band, and Jazz and Big Band. There are indeed some more polished and professional brass and wind libraries out there if you've got the bank-roll for them (and a dedicated hard drive, as they tend to get very large and otherwise resource demanding), BUT, you'll be very hard pressed to find one that covers so many families of instruments (even halicons, susaphones, euphonia, mellophones, flugal horns and cornets...in both solo and tutti configurations...and if you need marching battery percussion, and an even more robust set of symphonic percussion (school bands often call for more crazy stuff than one can shake a stick at, and COMB has a good bit of it), COMB has you well covered there as well!). It's also dongle free, so that helps out if you want to host this stuff on a portable rig! The libraries are small and lean in terms of system requirements, so you can even put them on a laptop or high end tablet and run with them! Garritan Libraries are quite inexpensive as well (given the sheer number of instruments they come with, plus the quality of the sounds is quite good if you bother to tweak them a bit in real time with expression maps).
Currently, you'll probably need to do some of your own expression map work with ANY libraries on the market (including HALion stuff). Just start with a clean slate on your first project, and keep adding on with each new project. With each and every 'technique' you enter in Dorico, you have the potential to reshape nearly every note in your score. It just takes a little awareness and practice of what your plugin(s) are capable of, and how to teach Dorico to talk to them.
Here's a quick and dirty rendering of a Fusion piece for Trumpet and Bone (Not my score, but it's rendered with HALion Sonic SE content that is included with Dorico). It's mostly General MIDI patches!https://drive.google.com/open?id=0B-9pj ... U1vekpjT28
When I can find more time next week, I'll try to do some Big Band, Jazz, Symphonic and Marching stuff and share some of the tips on how to get there (simpler than you might think).