I had the pleasure of attending a concert band music reading clinic yesterday and today. Lots of fun. We were encouraged to provide feedback.
In one piece the flautists complained their parts were written divisi even though they were "a wall of black." I gather that meant multiple bars, even lines, of nothing but sixteenth notes in leger-line country.
They recommended printing separate parts rather than writing two as divisi.
If the objective is to reduce paper, it might work to use two staves and collapse them when they're unison.
Anyway, write separate staffs where notes in divisi will be hard to make out. The musicians (well, at least the flautists) will love you better.