As long you are using different trumpets (Trumpet 1, Trumpet 2, etc) on the unison line, there shouldn't be phasing as multiple trumpets were recorded. I've never had a phasing issue myself. So I'm not sure what would be causing your phasing issues.
You should post these issues on the Garritan forum on this site.
I use JaBB all the time and have not had a phasing problem w/ unisons.
Here's some points ... because if you are not doing this, I can understand unisons getting phase-ey.
1.- If you are not playing the lines in (each trumpet part) one at a time, in real-time, you need to alter the start and end times of every note. I have not found programs to do this as well as actually dragging the starts/stops on every note.
2.- Add plenty of unique cc1 to each trumpet part. This helps a lot ... but you can't do it to trumpet 1 and copy it to trumpet 2, etc.
3. - Add unique vibrato to each line ... same as item 2 ... you can't have matched, identical vibratos. Also, even if you don't want an exaggerated (or noticable) vibrato, a little will still help your situation without changing the charactor of your lines.
I've never had to do the extreme detuning you tried, nor play with var controls (I would use those more for rapid-fire sequences of same-pitch notes).