This small mod makes minecraft leaves decay much faster. It should also be compatible with most modded leaves.
This mod is not required client side so clients don't need to have the mod installed if it's already on the server.
In the config file you can change the decay speed & fuzz (How random the decay is). There is also an option to make all leaves decay faster, by default only leaves on trees broken by players decay faster.
Feel free to add this to any modpack you want.