Moraxus is a hero that fills more or less the same role as Hammerstorm or Pestilence, just not as well, which is why you don't see him.
As for the BH situation, you didn't really make it clear whether or not it was ganks or facing him in mid.
With regard to ganks, you need to have wards and team support to deal with him. Meaning, your team needs to teleport to come help you. Either that or you need to have a teleport to escape with, since BH has no way to prevent this, just like arachna, warbeast, etc. He's only really an issue when he's way ahead in farm and levels, otherwise if he tries to solo gank you, you can just stand your ground and beat him up. Map awareness comes with experience, and since you seem to be getting ganked, try to pay more attention to the mini map/where the opposing heroes are to avoid getting caught in a vulnerable position.
As for BH middle, you need to take as much of his last hits as you can, both kills and denies, and harass the crap out of him. Creep kill healing is what makes him strong early on, so you have to prevent it. If he silences you, use that +20% damage to give him more damage back. BH is a very powerful hero in the lower brackets of play because he exploits lack of team play, map awareness, and easy last hitting. Take these things away and he's a virtually useless hero with nothing more than an auto-attack and a silence.
I played against a BH mid today on SS, take a look at match 61787427 for an example of beating one. I don't know what your rating is, but I'm guessing it's in the 1500s or 1600s, so the BH should be at around your level.
Also, a lot of players coming from LoL seem to have the mindset of learning one hero, playing them over and over. I'm of the opinion that you should play as wide a range of heroes as you can to gain a more comprehensive understanding of the game and see what you like/are good at. HoN's new FTP model makes this more difficult though, I don't know if you're legacy or not.