Yes, i would say you can have too much live rock..
1) it limits water volume
2) limits swimming room for fish..
3) inhibits flow as the water is not able to circulate the rock work as good as it would be able to compared to a tank that has less..
All you need to achieve good filtration for a tank that uses the rock as the filter is 1 - 1.5lbs per gallon of tank water in my opinion.
Niko