I do not play DOTA but I am familiar with the HR bots in LTD and how to make HR a serious gaming community.
My suggestion is to start the buzz about the HR bot rather than to split the stats on ENT's website to accommodate different game modes.The LTD HR bots started out at a desolate place where one could go to think in quiet solitude for nights on end but we eventually (as a community) got the LTD HR bots to be an active and well mannered community. How do you accomplish this? Well, by fishing of course!
In order to make an HR bot work, you have to have demand. Most players over 1200 ELO do not even know of the existence of the HR bots. It is up to the skilled players in the community who actually want a good challenge and a well balanced game to start making acquaintances in the community and inviting people to play on the HR bot. I am sure that there are many familiar faces in the dota community and a lot of players must know and recognize eachother.
Why not get 3 or 4 of you to agree to meet in the HR bot and wait in the lobby. Then one of you can go fish the public bots for more players. Meet new people in the process, make new friends and slowly fill up the HR bot to get a game started.
It may sound like a tedious process (and at first it certainly is) - but the rewards will be great. I speak from experience with the LTD HR bots and once we spent a solid week fishing and playing only a handful of games per night we eventually got the buzz around to make HR a nightly event. The game play is so much greater in an HR bot because there are no new players, no leavers and
rarely any hackers (I emphasize.. "rarely" - not never

). This is far more a test of one's skill then simply choosing a game mode designed for tougher play. You will be able to see who the top players really are by the HR ELO system. The bots are always a-bal and you can even set up some "ground rules" for the HR bot.
My suggestion once again - get the buzz out about the HR bot and make it an active community. I don't think that you will be dissapointed!