Another question I'd be interested to discuss is this: if the Cleric of Life is working as intended, and we agree that it provides the whole group with a CR multiplier, what is that multiplier?
I have yet to run a group with a Cleric of Life in it, but I've run groups with Lore Bards, who are actually much better healers than Life Clerics.
My informal observation is that healing magic is never indispensable (since HP is only a second line of defense; it's almost always better to spend movement than HP) but it is useful, especially for groups with high AC. The value of healing is essentially tied to how many rounds of enemy actions it negates, which is high for someone like an AC 23 Paladorc (with Shield for AC 28) or an AC 21 Bladesinger with Blur up, and lower for someone like a Recklessly attacking AC 16 Wolf Barbarian or other DPR-focused character. (Yes, damage resistance helps, but generally IME it just offsets the Reckless bit, and damage taken per round is still high.)
For a truly optimized healer like a Life Cleric 1/Sorcerer 3/Lore Bard 6/Warlock 5 (healing about 2500 HP per long rest plus 480 more per short rest) in a group with lots of at-will DPR (Sharpshooter fighters/rangers) and good defenses (say, a Mounted Combatant tank in plate armor and a shield), the effectiveness multiplier is about tenfold: instead of having 400 HP in the party, you have about 4000. For a life cleric the effect is much smaller, probably not more than double, and it doesn't affect an individual fight as much as it does the party's endurance over the course of an adventuring day. Your story about an eight-PC group taking down fifty enemies is about what you'd expect from any group, life cleric or not. Eight PCs are hugely powerful.
Edit: oh, wow, this thread is necro'ed and I've already responded to it last year. To explain the superhealer: the essence of the build is that a Lore Bard 6 can steal Aura of Vitality (3rd level Paladin spell) which heals 70 points over the course of a minute. Then Life Cleric 1 adds 5 points of healing per round, for 120 total, and then you use Extend Spell and a sorcery point to double it to 240 points of healing. Voila, 240 points of healing with a single 3rd level spell. Most efficient healer in the game, and none of the targeting restrictions which always make Preserve Life worth less than its theoretical maximum.