Tony Vargas
Legend
The trick here might be to make the class more of a helper in combat. So he hides and does something to distract an enemy or warn an ally. In 5e, you can generally use an action to somehow set up advantage or disadvantage, so the class might do that a lot - via an actual class feature, rather than improvisation as it's usually done. Imagine a Druid with Faerie Fire as his only combat spell, for instance (you don't have to imagine it, you could just prep your spells that way).The way it's been said to me is "I want to hide in a fight, and NOT feel like I'm cheating the other players. If I do it with a 3d6+1d4+3 attack sitting in my wheel well, then I am cheating them, and they are right to yell, just group with the fighter and stab the thing."
The character isn't 'useless' in combat, he just contributes in ways that aren't direct. Another, even more extreme, example might be the 'victim' character who's personally helpless in combat, but gives his allies bonuses and extra actions to come to his rescue. (Ironically, something you could do in 4e with, of all things, a Warlord build.)