FrogReaver
As long as i get to be the frog
Well, you're forgetting a few important issues when it comes to darkvision that are more important:
1. When such situations do arise (and they will in most games IME), the party members NOT in armor are likely the first targets of that ambush salvo. Now, if your caster-types have Shield, they are probably not too badly off.
You have an odd idea of general enemy tactics
2. If you shot your Light-Arrow at the enemy, it only takes one of them one action to smother it.
It's lit by the light spell. The shaft of the arrow illuminates light. Not sure what they are smothering a whole arrow shaft with...
3. The most important issue with darkvision (in any case), is most creatures with it have a sight range of only 60 feet. Not very far at all.
No idea what this has to do with anything?
How these scenarios play out depends a LOT on the DM and players (strategy and experience and so forth).
My point was, as I stated, those two characters will be a liability at some point for not having darkvision. How much? Who knows? That depends on the table. And FYI, I do give darkvision a lot of weight as being able to see when others are potentially blind is a HUGE benefit IMO. Maybe not at your table, but it always has been at every single table I've played at.
And my point was that the liability can easily be overcome which makes it not so much an all the time liability but a minor inconvenience. That seems to be the level darkvision is supposed to be at.