Heat metal also has limitations: only affects metal, range is only 60', requires bonus action to use each round. The last two items are the most important. I had a druid player who liked to use this, until he found his targets would often run away or hide. He couldn't stay within 60', or he couldn't see them, so he couldn't use the bonus action. Of course, if the target does move away, that's useful. Is it worth a 2nd level spell? Depends on the situation. Again, a spell that's good at times, but not overpowered.
I agree on the granularity portion, and that is the price that is paid for simplification of modifiers. The same concept applies to Drow having sunlight sensitivity, etc.It's no worse than Fog Cloud, which does the same thing for ranged attacks out of the cloud (due to the way the heavy obscurement rules work) with no save.
If you have a beef here, it's probably with the vision rules and the granularity vel none of advantage/disadvantage.
As a DM, you should have intelligent foes seek advantage and seek to impose disadvantage in the same way. Skilled tactical combat largely involves trying to manipulate battlefield geometry and gain advantage, moreso than making attack rolls. Have enemies toss nets, hide in the dark while firing (with advantage) at targets illuminated by one Dodging enemy carrying a torch, push enemies prone or off cliffs, etc. Faerie Fire fits into this scheme as one pretty good option, but certainly not one that cannot b e countered.
Unintelligent foes are not supposed to be a real challenge anyway, so it shouldn't matter if PCs find an exploit against them and exploit it to the hilt.
It's no worse than Fog Cloud, which does the same thing for ranged attacks out of the cloud (due to the way the heavy obscurement rules work) with no save.
Range is only a limit to cast the spell, not use the bonus action. At the top of page 203 of the PHB under spell range it says "once the spell is cast, its effects aren't limited by its range, unless the spells description says otherwise." So having cast the spell the Druid doesn't have to see or be within 60 feet of the victim - just use a bonus action to make them burn.
in theory the Druid can cast the spell within 60 feet then spend every round running away and hiding and a bonus action to burn the recipient of the spell.
if you are in a fog cloud you are in a heavily obscured area which means you effectively suffer from the blinded condition (p183 of PHB). Is there something I'm missing?
https://media.wizards.com/2016/downloads/DND/PH-Errata-V1.pdf said:Vision and Light (p. 183). A heavilyobscured area doesn’t blind you, but youare effectively blinded when you try to seesomething obscured by it.