In regard to your question about S&W gunsmiths, I've only had one revolver noticeably out of time - it spit back at my face (I always wear shooting glasses). It's been back to S&W twice for that and accuracy issues and likely going a third time. It's a .22 J-frame. I know that there is crap .22 ammo, and I've shot a fair amount over the years, but it seems magnified in that particular revolver. So to answer your question about whether or not S&W gunsmiths can fix timing, consider all your options. I only deal with them because the gun is under warranty.
Don't necessarily give up on local smiths but at least talk to them or visit to see how experienced they are with wheel guns. If you don't feel comfortable, send them out to Hamilton Bowen, TJ Custom, or some of the revolver gurus others have suggested. The art of revolver smithing is a dying art, and it seems like S&W's designers are more focused on drop in parts replacement than had fitting. I talked to a student from a popular gunsmith school about revolvers and learned his interest was more to be able to assembly AR kits and builds than actual gunsmithing.