It isn't clear what is your real problem... The load isn't balanced correctly or one of the 3 nodes is very slow?
the load is balanced correctly for the initial 3 instances but we created additional instance on each server, which is really slow.
Scenario is :
Day 1 : We were running JBOSS 3 instance on port 8080 - due to huge volume the server is not able take the load and started crashing.
Day 2 : We created additional instances on port 8280 - now two instances are running on each server.
the second instance is responding very slow. Please shed some light.
If the 3 new instances are slower the old ones it means that they aren't configured correctly,..
Additionally if you have just put them on the same already overloaded boxes I don't think you are going to see any improvement on the answer time of the whole cluster.