After some testing; I found out some interesting facts about Cluster Rockets, hope they help! Thanks to Adiktuz for well...inspire me to test the ability, again.
First thing I found is the Max Damage is not the total damage the ability can deal.
I set the damage amount to 100; max damage to 100 and interval to 1 - which supposed to make the ability deal only 1 instance of damage. It does; however, the max damage is shared between unit affected. Meaning if you hit 2 units; each of them will only receive 50 damage; and 25 damage if you hit 4.
Next; I changed the interval to 0.01; which supposed to make the ability deal 101 instances of damage, capped at 100. So by the theory above, each unit should only received 100 damage no matter what. However, when I tested it, it instantly raped the Acolyte! After a few more test, the conclusion drawn is: the Max Damage only applied to EACH INSTANCE of damage from Cluster Rockets, which means the total damage the ability can potentially deal is not the Max Damage value.
The last thing I found out: you can stop Cluster Rockets from dealing damage. Simply stop channeling it. If you do that before the first missile reach the target point; the ability does absolutely nothing.
Hope these info help you on bug fixing and such.