I actually may have previously done this and forgotten about it.
Currently the 3 spells are varying levels, varying slow values, and around 30 seconds long. Para is typically the one used once it's learned.
I propose that they be changed to the following:
Cramp: 10 value, 45s duration
Fracture: 20 value, 30s duration
Para: 30 value, 15s duration
This effectively nerfs slows as a whole, while also creating diversity on spell choice. Although Para, especially when chained, will largely cripple a player, the Cleric can choose duration over value to keep an enemy out of the fight for longer via Fracture or Cramp. This also would possibly allow increased viability of alternative specs.