Sometimes it happens so fast I barely even have time to go hit the bedroll, especially if I have to select that particular character because they're far from the currently selected character for bedroll to reach, and especially if there's two+ characters that are about to DoT to death. The bedroll is insant, but I still might only have a second to hit it. It's not a huge deal, but just a little irksome when it happens and it feels like I was screwed because the game went into real time. Guess you just have to try and heal your characters to levels where you can react to heal them before they die.
Yeah, it's not perfect. I had a character die to post-combat poison damage after writing that

, but that was because I pre-buff bedroll and it was still on cooldown after the fight.
I have a bedroll on each character and have it hotkeyed to #1, which helps a lot. If characters are chained and not too far away (and not on cooldown) it heals all at once.
I would really like to be able to pause the game and issue commands when outside of combat. This would be great for the problem you described and make initiating fights and careful positioning a lot easier for a single-player managing a full party too.