You don't need diamond pipes. BC pipes will always distribute evenly between valid routes in a junction so you could just have the pipe go to a junction that split the items into four pipes and split those pipes into two each so you get 8 pipes with even distribution of items.
They distribute somehow, but not evenly. I think all items in a certain timeframe go the same direction. So if a lot of coal arrives it will mostly go into one direction. To reach a equal distribution with BC you need a constant flow of items.
Its not the overflow Im worried about. It's the speed. 8 macerators can process 1 coal/each faster than 1 macerator can process 8
Since you feed the Macerator with an MFE you are quite limited in speed. To make it really fast try 15 overclockers and feed them about 2.000 EU/t they will finish a process in 1 Tick, so you can macerate 20 coal in 1 second. Since the compressor can only compress for every 8 coal it should not be the bottleneck. But since the Macerator eats 2 EU/t you can only use 8 Overclockers if you feed them with an MFE, since 9 Overclockers need 137 EU/t, while 12 would eat about 560 EU/t.
Have you used an EU reader to check that the amount of power coming into the machines is definitely 128?
The EU-Reader tells you nothing about explosions, since there is no limit to the amount of EU a cable can transmit.
Yeah each one gives you like 10K EU so 4 is 40K EU on board 64 would be 640,000 EU which yeah I have a feeling there is something about how they discharge that is your issue.
Propably. They might end up sending pakets inside the machine that are over 128 EU. But than this should also happen with a single upgrade, since 10.000 EU is enough to blow up a machine. I really never bothered about them since all you ever need is a single storage-upgrade if you want to use 13+ Overclockers. Since Gregs limits you to 4 upgrades per slot I normally go for 12 Overclockers and 1 transformer-upgrade (sometimes 2, but since MFEs are so cheap, they normally do the job quite well).
Storage upgrades are only usefull if you power machines with rechargeable stuff like batteries... but really nobody uses machines that way.