Traditionally when a monster fails a save against a spell like hold person, they can then make a new save at the END of each of their turns to break the effect. I have been surprised to see paralyzed bugbears and gnolls make a saving throw on their turn to break the effect and then immediately charge forward to attack on that same turn. With this mechanic the monster needs to fail the save twice in a row (once when cast, again at the start of their turn) for there to be any effect at all. This makes hold person very much not worth a 2nd level spell slot. I haven't yet tested this with similar spells.
