I think your assessment is spot on for many combats. However, SS+CBE brings several quality of life improvements (negating cover, etc) that allow any character to maintain effective damage across a wide variety of situations. It even feels more fun.
Speaking generally now, SS+CBE is definitely a powerful combination. But I'm honestly torn if anything needs to be done about it at all. It empowers a very specific kind of build that most people might play once or twice, ever. Maybe the combo will rotate between players from one campaign to the next. If it happens in your campaign, the easiest answers is to shrug and let the player have their fun. Just make sure nobody else feels bad.
If I absolutely must do something to improve the balance, I would change SS to this:
Sharpshooter
You have mastered ranged weapons and can make shots that others find impossible. You gain the following benefits:
• Increase your Dexterity by 1, to a maximum of 20.
• Attacking at long range doesn't impose disadvantage on your ranged weapon attack rolls.
• Your ranged weapons ignore half cover and three-quarters cover.