Honestly the best solution IMO is to just give Credo's tiers based on the amount of previous credos they require to get there. Increase the number of quests required by tier (rather than the number of Credo's you already have).
Also, make suiciding non-viable as a method of cheating credos.
With 5 potential tiers that means there would be:
Tier 1 (fisherman, forager, hunter): 2 quests per
Tier 2 (Quarryman, Farmer): 4 per
Tier 3 (Gem Hunter, Miner, Mystic, Etc): 6 per
Tier 4 (Pearl Diver, Strider): 8 per
Tier 5 (Blacksmith, Cavehermit): 10 per
I'd even be ok if they required more quests each than this overall.
On the other hand, if they just removed the suicide loophole I'd be happy to. I don't mind the grind.