Looking into my campaign notes, there were several notes about Balrogs from the 'In The Cities.com' blog. And these horrors lured adventurers into traps when they were in the line for wilderness encounters. My advice when using Balrogs is to be very careful. There are were several TPK's in which Balrogs were used.
When we go back into the early days of OD&D then we encounter the Balrog as a viable OD&D monster at least before the Tolkein estate lawsuit. When it comes to Bloody Bloody Arduin just below the Balrog is the Valpyr. Several steps above the lich but well below the balrog in the scale of the damned. With the return of Emperor's Choice now back the Valpyr miniature is also back on the menu for ordering.
In the ACK's Heroic Fantasy Handbook there are the cacodemons who fill the niche of the high ranking mid management demonic entities.