There are some unclear statements and unproven assumptions in the question. Thus an answer in a general way:
Load balancing in BizTalk has two aspects: network and hosts. Load balancing method depends on the host type: in-process vs. isolated.
BizTalk Server Monitoring Management Pack has capabilities to monitor health of the BizTalk artifacts.
Generally, network load balancer should not pose a problem for the performance as it only polls once per server (not each BizTalk host).