I would expect so because of two factors:
1) It's a Concentration spell, and you can't cast another one whilst maintaining it. Many of the casters who can cast Heat Metal have superior alternatives to cast instead.
2) 5E monsters in general are absolutely not designed with bizarre hit-and-run corner-case scenarios in mind. They're designed with combats in mind. They expectation is that they stick around. Many of the ones who can cast this spell have a ton of other good spells, or other good abilities, or do significant damage, and they're throwing that all in the trash if they run. Mistwell keeps mentioning humanoid casters, but if those casters can cast level 3 spells, they have superior alternative uses for Concentration unless the DM designing them decides they don't - in which case it's on the DM as the designer. Hell, there are situations where, realistically, Bless will inflict more damage on the PCs than this will (albeit usually only if the caster is grouped with some pretty serious hitters).
I think it would be reasonable if this abuse/exploit is going on to limit to maybe 150' range, but that's the only change I could see being needed or beneficial.
Enemy bards, clerics and druids are "bizarre hit-and-run corner case scenarios"? I run my NPCs as intelligently as I think they should be. If that means casting heat metal and then hiding behind full cover, that's what they do. But I've experienced games where heat metal was the de facto spell to be cast against armored opponents by the PCs.
As far as range, according to sage advice once you cast a spell you can maintain it even without line of sight.