Not going to lie you lost me when you said ambush doesn't work with burst and to take trap expert.
Ambush does work with burst just to let you know.
I will give you an example of what pistols are capable of, and you can tell me if they wouldn't completely overshadow the sniper part of a sniper/pistol build.
https://youtu.be/f-GyGQBN8s0I have no doubt about Pistol and Sniper being strong together, but pistol fills the same niches as sniper AND fills its weaknesses. Too high ap cost attacks? - bullet time! enemies close? - no melee penalty! need to move and shoot? - no movement penalty!
Smg does the same but doesn't have the strengths of range, single target damage, good crit damage, and high special attack damage like sniper does, that's why they go well together they cover each others weaknesses instead of overlapping and overshadowing them!
Sniper/pistol is strong especially with your version of traps tm gas and whatever but that's not the point of the build I was trying to make. When I ran this build I couldn't place a 2 layer deep trap wall to stop all enemies from ever reaching me, it was meant to be a sniper build with a sidearm that complements and that's how it is, allowing it to operate at ranges not specifically planned for with meticulous trap placement and stasis. It was the first psiless ironman recorded and its a fantastic build despite being psiless. Perfectly balanced each weapon in harmony with each other.
If I had a pistol with bullet time, ambush, and crit power - where does the sniper fit in? My opening salvo with pistol would be much stronger than with sniper past the first 4 shots, 4ap attacks, 1 shotting each enemy and 2-3 shotting bosses. Sniper would essentially just be a vanity weapon at this point. If your pistol wasn't doing this you were playing very sub optimally, it is not hard for pistol to achieve this even very early on.
Cheers!