On second thought, there may be a bug here... will investigate tomorrow.
About this, I have confirmed there is a bug in 2.7 where it can get into a situation where it can't queue enough work and continually thinks one pool is not providing enough work. I have fixed this in git but this has introduced a new crash which kano is trying to help me track down. In the meantime, anyone on 2.7.0 should probably enable --failover-only to mitigate its problems.