Well, the shotgun example was just that - an example. Shotguns cover closer combat much better than either snipers or crossbows, so you can still make stealthy takedowns from range, but there will always be situations when you'll have to fight close quarter. Shotguns will shine then. Think of them as pseudo melee weapons which benefit from your Guns skill.
As for the particular build you've posted - I'd do it like that:
http://underrail.info.tm/build/?AQYHBQQJAwYPDwAAAAAPAA8ACg8ADwAKAAAAAAAACico3787 Dex is for Quick Tinkering. Any build that says they want to do traps needs this perk.
No need to max Stealth because you'll get Stealth bonuses from equipment. As the game progresses, you will be able to put more points there, but keeping Stealth maxed at all times is a waste of skill points, imho. That is not to say that you don't need it, just that you can spend your points more optimally.
Same goes for the Traps skill. Even though you're a Traps build, allocating too many points into Traps is a waste. You need 25 points to take Quick Tinkering, after that put only as many points as you'd need to use a certain trap - no more. Your high Perception will help with Trap detection, so you have nothing to worry about.
I know that new players love Lockpicking and Hacking, but between the two I'd advice to choose only one and use the points in Crafting. Crafting will produce much better results than either/both Lockpicking/Hacking in the long run. There are benefits to having them, but Crafting is just downright better.
Speaking of crafting - try getting 50 Effective Chemistry as soon as possible. You will love MKIII Frags/Flashbangs for after you've started combat from Stealth. And there are a plethora of other tools available from Crafting that will make your life easier. Your Throwing skill will help you land Hunting Nets, as well, which will help you control choke points and doorways.
Always try to put as many points as you can spare into Mechanics because that skill will give you the best Shotguns and Snipers in the game.
Mercantile will help you with shopping and opening special stores which will have parts for weapons and armour you'll need.
As for perks - take Grenadier, Quick Tinkering and Sure Step as soon as you can. Consider taking Aimed Shot and Leading Shot after that. Sixth Shell is quite decent to have.
PS: you playing Warframe, by any chance?