The point of fleeing the fight is that your story is not over which it would be if the whole party was wiped. So you can pay Withers to revive the dead companions in the camp. A problem exists when a companion is not dead but down on the ground and still alive in stabilized condition. In this case you cannot long rest and also not revive them with Withers, you have to crawl back and bring them to their feet with a healing spell. Luckily the enemies in most cases kill downed companions.
If you don't want to revive a dead companion, you can ask Withers to take them into custody, so they can remain dead for a time. Never tried that however. With lvl 5 you should have enough money to revive. I had to flee from the Gith fight, all rolled first and killed/downed two of my chars and took the third into Hold Person, and killed him in the second turn. I ran away with the low hp fourth char, revived the three others in the camp with the aid of Withers and retaliated. The 600 gold lost was a bad hit, but better that than losing the whole campaign.
