Improper removal of SQL Server cluster A node was evicted from a windows cluster without first uninstalling the sql first. When the node was put back, an error was produced when we tried to failover. It was reporting a missing dll. Feels like removing the node before uninstalling sql from it has corrupted or deleted part of the build. 

Has anyone else encountered this situation? Can this be repaired or is it best to uninstall the sql from the node and start again installing a new sql node.  

Thanks!
I would first run a repair installation of your SQL Server installation on the node that was evicted.  This should at least get the appropriate binaries installed.  Then, run a Discovery Report to validate what is and is not installed.  If your SQL node installation is no longer available, the reinstall the node.