1 node getting 100% cpu usage, other nodes in cluster 10%

I launched a 3 node cluster using the Cloudformation templates found on your Github repo. We created a new bucket, Couchbase with two replica sets. In our app we point to one of the nodes, call it node A. We started stress testing our app backed by Couchbase, we saw increased CPU usage and ops/sec on all the nodes, but Node A eventually spiked to 100% CPU with the other two nodes not going above 10%. It doesn't seem like the requests are being distributed.

Is this expected behavior? We're using the couchbase PHP extension and an unmodified install of 1.8.1 from the Cloudformation templates.