Looks like this is gonna be a good time for HoN. Apart from the 3.0 update, someone has released the dll files required to play HoN on a LAN/online environment which is also custom map friendly. I've been jamming valkyrie wars for the last few days. Best part is only the host requires the modified files, so if client has the map, they can connect via the IP address.

So custom maps as of now is fully playable. Know another 1 or 2 mappers that also started working on their maps again because of this.
Can go mad now, and play your creation with other people. Also jammed my Nightmarish map with someone, without any real issues.