Overall, I agree that the fight either is on the border of TPK land or is firmly in OK land. The only exception would be is the DM has monsters regularly Coup-de-grace PCs that are down; he's going to see lots more individual deaths.
Thanks for the comments!
You hit on part of why
Nail & I have been discussing this. The party has been charged with finding out what happened to a lost caravan and tracked a couple of the wagons to a Hobgoblin cave. So far they've mainly fought disorganized goblins, various beasts and several varieties of undead who have all focused on any healthy living PC rather than CDG anyone dying.
A couple sessions ago they were trying to cross a river in a forest as the Ranger was tracking the wagon trails (not terribly difficult with Perception rolls generally in the high 20s

). Said Ranger rather boldly skipped across the log bridging the river and battle was joined when 2 Hobgoblin Archers, 2 Hobgoblin Soldiers and 3 Dire Wolves burst out of the trees in ambush. The Defenders and Leaders had some difficulty getting over there to save the Ranger's leather covered hide but she made it out safely within a round or two.
Unfortunately for the party their placement on that bank of the river allowed the hobgobs and wolves to gang up on the Swordmage & Fighter. The Swordmage fell dying
6 times but before I could have one of the Soldiers CDG he was healed each time. The party was victorious but after the battle I made a point of telling the players that the hobgoblins were much more systematic and regimented during combat than any foe they'd faced so far, and that in future battles most any Hobgoblin given the chance would likely try and CDG a downed PC.
Similarly there are some beasts which are described in the MM as likely to just try and drag off a dying PC for a meal rather than stay and fight the rest of the party. If the beast can drag a dying PC away from the battle a bit then I think a CDG would make sense as it starts to eat the PC for dinner.
Those are the only situations so far in my campaign that I think CDG will likely be used, so I don't think it'll happen
regularly but I would guess I'll have a few opportunities as they continue to battle the hobgoblins in this cave.
Nail mentioned brutal honesty sometimes coming into conflict with sense of immersion. In the hobgoblin case I wanted to be clear with my players that the hobgoblins seem to follow a different set of priorities in battles compared to other foes they've fought so far. At 4th level I figure that's something the PCs would know after facing the hobgoblins in battle, so I thought it important information to give the players, too. I'm hoping/expecting that in future battles with the hobgoblins that helping a dying PC will become a much higher priority for the party than it would it most other battles where, to date, I've only seen them concerned when a PC has failed 2 death saves already (which hasn't happened in 14 session so far) or is taking ongoing damage repeatedly).
Thanks