I'd second that; OCS works on a Pool/Farm basis for increased capacitty of availability, Clustering is not an option.
There are some very good value Load Balancers available; the most import things to watch for are Source NAT and Appropriate throughput; which could be quite high for any enterprise setup requiring More than one server for capacity.
If Your goal is resilience, look into increasing hardware resilience or using a redundant server chassis.