IMO, VE Pro is an absolute must if you are doing composition with the number of players of standard orchestral ensembles in Dorico (outside of NotePerformer).
The way people use orchestral libraries in DAW’s is first you set up a fully balanced template with EQ’s, compressors, gain plugins and aux buses for reverb. A good template will also use numerous group tracks, ex. you might have OT Flute 1, OT Flute 2, OT Flute 3 all going to a group track called “OT Flutes” and that as well as other similar group tracks might go to a group track for “OT Woodwinds”. You might have another woodwind library, say VSL Flute 1, VSL Flute 2 that go to a group track called “VSL Flutes” and that goes to a group track called “VSL Woodwinds”. Then the OT Woodwinds and VSL Woodwinds might have their own FX settings and level adjustments to equalize the balance and make them sound as similar as possible, and then once they sound pretty much the same, routing them to a single stem (another group track) called “Woodwinds”, then at the very top level all of the main stems “Strings” “Woodwinds” “Brass”.
All of these tracks can have their own FX plugins on them of course. Sometimes they might be up on the individual instrument tracks, other times they might be on a group track. But the idea is that you put the time and effort into balancing this and getting it sounding right.
Using Dorico by itself for this has numerous limitations. First of all, no group tracks, so you can’t set things up in the way you normally would in a DAW. Want to boost the level of all woodwinds globally with 40 different tracks? Sorry, no group tracks, so you have to manually boost the level of each one one at a time, and if you haven’t boosted it enough or boosted it too much, you have to go through them all again to adjust it.
Now that you have done all this, built a great template directly in Dorico working around the limitation of no group tracks by putting in 5 times the time/effort you would in a DAW. Now you have another piece you want to apply this template to. Sorry! You can save the endpoint config and make that a template, but you lose all your nice balance/routing/insert effects. So now you have to go through all 100+ audio channels in Dorico (assuming here that you are blending multiple libraries from different vendors together) and manually re-add all your plugins. Then you have to do that again if you want to write another piece. Insanity.
Instead of doing this crazy thing, what you do is set up VE Pro, and you use that as a mixer, hosting all your instruments in there, and just send back a single audio return to Dorico, and then don’t use the Dorico mixer at all. The VE Pro mixer is equal to that of a DAW, so if you host everything in a single VE Pro session then you can use that mixer for absolutely everything and pretend the Dorico mixer doesn’t exist. The VE Pro mixer supports group tracks and aux tracks and everything, so you can set everything up the exact same way that everybody sets up templates in a DAW. Want to apply this to another project? No problem. Just plug in the same VE Pro project (you could make it an endpoint config and template) in the other file, and all of your inserts/sends/routing, everything gets transplanted to the other Dorico project.
The single-instance VE Pro setup makes a ton of sense for single computer composers in this particular case.
The only time I would not suggest this is if you are mainly working with NotePerformer and don’t really use instruments outside of that, or if you are working with smaller ensembles mostly where this group routing is unnecessary, or you might also get by without it if you are using only libraries from a single vendor and they already sound exactly the same and are prebalanced correctly then you might also get away without it (I haven’t found any libraries where the balance is 100% perfect out of the box though). In any other case you definitely want it.