Distcc will fill syslog by default. I propose to add this option to default /etc/conf.d/distcc file : DISTCCD_VERBOSE="0"
distccd does not use the DISTCC_VERBOSE envvar. try setting --log-file /dev/null in the options in /etc/conf.d/distccd i like to leave this "verbose" since it helps when users have bugs that may be hard to reproduce.
Of course, verbosity is good. But any package propose debug info by default. It should be only enabled when tracking bugs. This option could be presented as a debug option in the conf file :)