As a DM, the rules-as-written are more a suggestion than rules. As long as you’re consistent with applying your modified rules, give that Barb an Intimidation bonus based on STR or whatever you like. I have a pretty decent sized list of rules I treat differently than RAW, because some spells and abilities are never used - why cast anything else when you have access to Fireball?
That’s the way I handle it. A 1 on the die is automatic failure, but roll again and on another 1, it’s catastrophic.