Man, stop fussing. This isn't a competitive online game. It's a fun story driven game. 
I love that headband. I can do stupid fun builds with it. 
Build a STR/DEX/CHR Warlock and go wizard spec at level 4.. You can literally do anything in the game from there just by learning spells. And have a blast doing it. 
I also like soloing on runs to avoid the team mate drama. I've already seen it lol, I don't always need it. With that headband I can have a blast. 
And while it may seem OP to the 'purist' people out there... How will it scale late game? (I'm not a DnD person so I don't know how DnD leveling works). But either way... just sell it if you don't like it and find something that matters to complain about..