Quite frankly, your tools suggested the split, but because that tool knows nothing about usage from the subscribers on that node, you were not told how to optimally split the node. You were expecting a 50/50 split in traffic after the activity, but the lack of intelligence and guidance has caused you to do something more like 80/20. The tool you used did not perform enough analysis for you, so how could you know which subscribers to move onto which nodes? Then, how do you perform any kind of past and future trending to see where the split would be effective? You are back to square one.
With currently technology, you can make long-lasting splits that will give you a split as close to 50/50 as possible. The same tool can run the analysis, and tell you how long before the next split must be performed. Make sure you always use a tool that can guide you as much as possible. Guessing should not be a way of doing business.