Toll the Dead is one of the strongest (if not) damage cantrips IMO due to the d12 and using WIS saves instead of CON (which most creatures would do better with...). The potential 6d8+STR for Blessed Weapon equals the d12 version for Toll the Dead, but you don't
always get the d12... So, I like the idea posted upthread about it doing a d4 (or
maybe a d6?) instead of a d8. The d6 is probably fairer IMO.
Although it might get a bit fiddly, making it d8 (weapon) + 2d8 (Divine Strike) + 3d6 (Blessed Weapon at tier 4) average 24+STR mod. If you are a melee Cleric, odds are that would be +3 IME, would make it 27. This is the average of
Toll the Dead doing d8 half the time and d12 the other half assuming a WIS 20. (4d8+5 avg. 23, 4d12+5 avg. 31; 23+31 = 54 / 2 = 27.)
Anyway, I am still waiting to see
precisely what this cantrip is meant to do.
It seems like the primary intent is to make a cleric's attacks magical with a melee weapon, but has since then gained additional damage as well...