Firstly, you have more than 30 cards listed.
Void Terrors can be good, but the only thing you've got to really work with them are Loot Hoarders, and while the occassional 5/4 for 3 and some silence vulnerability is nice, it's not great. And it's more situational.
Currently, including the Void Terror, 15 of your cards are minions of 15 mana or less, and you have one 4-cost minion and eight 6-cost minions.
This is a fairly unbalanced curve. Those 6-cost minions can be good, but they can also clog up your hand, and if your cheaper minions are controlled, such as through superior draws or AoE, then you might have to wait a turn or two before you can even start playing those 6-costers... and you'll only be able to play one of them at a time.
Most of the cheaper minions won't have much impact on the game at that point either.
My recommendation, aside from figuring out a card to cut to make sure you only have 30, is to figure out what sort of mid-game cards you might want. Another Defender of Argus or Hellfire could be very good for example. A lot of people like Dark Iron Dwarf for more aggressive minion-based decks, and I know I've always liked Azure Drake for more control-based decks and play-styles.
Even if you want to keep your deck heavy on the 6-cost minions, it is important to have solid mid-game options, even if it's just to stall out longer till you get them.
Anyway, I hope that helped, and didn't have too much Jargon in it. Ultimately, with this game the most important thing is to have fun. It can also be very helpful to experiment, and to identify what sort of over-all playstyle you are most comfortable with and enjoy the most, though that isn't always easy, especially if you're relatively new to card games in general.
Good luck. Feel free to keep asking questions.