Max Number of default simultaneous persistent connections per server/proxy:
Firefox 2: 2
Firefox 3+: 6
Opera 9.26: 4
Opera 12: 6
Safari 3: 4
Safari 5: 6
IE 7: 2
IE 8: 6
IE 10: 8
Edge: 6
Chrome: 6
The limit is per-server/proxy, so your wildcard scheme will work.
FYI: this is specifically related to HTTP 1.1; other protocols have separate concerns and limitations (i.e., SPDY, TLS, HTTP 2).