The Ensemble Routing architecture (presented at ANCS 2010) implements multipath routing for data center networks. Rather than managing individual flows, ensemble routing manages flows in groups or ensembles to provide scalable responsive management using simple hardware. Ensemble Routing combines: routing VLANs that define a set of diverse paths through complex networks, and load balancing algorithms to split traffic among those VLANS and optimize traffic flow. This extended abstract describes improved algorithms for the formation of routing VLANs and traffic load-balancing for Ensemble routing. The VLAN formation algorithms are improved by incorporating traffic flow estimates into the VLAN formation heuristics. The previous load balancing algorithm using a greedy heuristic is replaced by linear programming that determines optimal traffic splitting among VLANs. Simulations show that these mechanisms significantly enhance performance.