I probably will Sunday during the football games.
Off-hand, just looking back through the spells quickly, something like Hold Person is a good example.
You cast Hold Person just before ambushing your enemies or busting down the door to a BBEG.
You hit. BAM! Auto-failed Hold Person and the target is helpless until the end of its next turn when (maybe) it will be free.
If you have any remaining attacks (which you would if you can cast Hold Person), they are now auto-crits. Any of your allies melee attacks are auto-crits.
Combine this with smites or sneak attack damage and oh boy!
That is why I think it is too strong as is. Just imposing disadvantage on the attack is powerful enough IMO. So, I hope you will definitely think it over more.