Ash Zealot and
Tunnel Ignus are very meta dependant. Think about their value in your playgroup.
Mondronen Shaman feels a little to expensive manawise compared to what he does.
Fevered Visions is an interesting card, but be careful when you allow all players to draw. This may help them more than you.
Stormbreath Dragon seems nice, but you'll have to spend 13 mana in total for his effect, and even then its dependant on the number of cards in your opponents hands. I think there are more efficient options if you really need the damage.
What proved kinda effective for me in EDH is
Darksteel Mutation and
Imprisoned in the Moon. If you play one of those at your opponents commander, its usually way more effective than just killing them, since usually has a bad time removing them, unless he draws a enchantment removal.
Btw, there is another nice idea:
Tsabo's Web. This card is also very meta dependant, but if your playgroup likes utility lands, it might be worth it.