Multiprocess support works in general pretty well but isn't perfect.
Daemontools-encore still has issues with KILL signals, with HTTPD and MPMs a KILL signal will kill the master but workers often go to init and never stop.
What HTTPD are you running? If you're running one that does its own child process management (like nginx or apache), you should explicitly disable process group isolation via a ./no-setsid file.
http://untroubled.org/daemontools-encore/supervise.8.html