Voracious dragon isn't really the best choice here. Sacrificing half of your field to the dragon to try to win the game next turn sets you up for an easy X for 1 with any piece of targeted removal.
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This deck can't let the game go late or else it loses so "end game staying power" isn't helpful here. You should also pick up a set of Inkmoth Nexus.
I feel like you'd want to up the number of ziggurats.
put the flings in sideboard for matches with bigger creatures. You'd rather have burn spells to get in the last few points of damage than fling. You aren't running something like kiln fiend or the red souleater so it's really not being used to it's best potential here.
the boots aren't always a good answer. A deck like this isn't running enough creatures to justify having equipment. Hexproof is a great ability but if your opponent has removal in hand they just do it in response to the equip. You lose twice here by paying mana for the equipment and the equip cost instead of burn to pump the fiend.
This deck needs a lot of work. You don't have enough sources of infect to get you there. Replace the tormented souls with phyrexian crusaders. The Dark Favors would serve you better as steady progress, to draw more cards or distortion strikes. If you go with the distortion strikes just get rid of the invisimancer and focus on something like hand destruction or counter spells. And you need 4 contagion clasps, anything less is doing it wrong.
get rid of the tormented souls as they don't get pumped by your zombie lords. Zombie goliath isn't that great outside of a limited format and Gravebane Zombie actually hurts your deck. Try to replace brink of disaster with better spot removal like doom blade or go for the throat. Eradicate and monomania would be better used as better hand destruction like duress or despise. You should also consider reassembling skeletons which interact pretty well with Demon of Deaths Gate. Black is also huge for card draw with cards like sign in blood, or phyrexian arena don't forget those guys.
You need to replace the goblin tunneler with goblin guide. Replace the infiltration lens with ornithopter, and don't forget goblin bushwacker. In a deck only running 20 lands you don't want to have 8 of them coming into play tapped so drop the spires. Searing Blaze is also harder to cast for full value without fetchlands so you could consider something like incinerate.
Drop the grindclocks for mana leaks and get 2 more jaces. Other than that the deck looks pretty decent.
If you're going to run Brand in the deck you should run some fetch lands and a few mountains to be able to use it a bit more consistently.
Thanks for the advice, after more playtesting I realized that the suture priests need to be replaced. After looking at your list I saw that Kor Skyfisher is perfect. And I like burst lightning over searing blaze as it's much easier to cast.
Yes you need the piledrivers, legacy goblins are good because they have so many threats that can be dropped on turn 1-4. It's hell for control players and makes aggro decks have to empty their hands when they don't want to. Piledrivers just get massive if undealt with. Also the raging goblins are really subpar in this format, replace with a 4th guide a 3rd Instigator and the 4th sharpshooter.
Get rid of the charbelcher, that is a card you build around and is generally too slow for legacy goblin deck. Also 20 lands may be a bit high for goblins, and you should consider running Goblin Guides, Goblin Piledrivers and maybe a Warren Instigator.