Reminded me of an old Reddit post (the old database is still useful to search for) showing Gandalf's true nature. Dude wasn't a wizard, he was a multiclass fighter with an 18 in INT.
You really think any of them were high enough level to take on that Balrog? He was looking out for them! No group XP in LotR, otherwise Gandalf could have spent a few days powerleveling them beforehand.
Also they were on similar level, Gandalf and the balrog, it's a boss enemy he'd be on fairly equal footing if he was allowed to be his full divine abilities. The rest may have been able to take it on if they were willing to die, since I believe that's the only way that balrogs were killed in the past by great elf warriors.