The problem with monodarkness against arena is that most arena decks either have a lot of control or are fast. Bronze is especially filled with immodecks which are consistently faster than mono darkness. However, a way to defeat rushes are to heal similarly to the amount of damage they do. A good card that has excellent healing qualities in darkness is liquid shadow. Since it heals based off your current attack, then a good creature to use it on is Black dragon. When you need to heal, you can play it on your own dragon and sap up the health. Early on, you can also use it on the opponents creatures such as lava golem and phoenix to kill them before they can damage you too much.
A deck that I've had moderate success with is this deck:
Hover over cards for details, click for permalink
5uk 5uk 5uk 5uk 5uk 5uk 5uk 5ul 5ul 5ul 5ul 5ul 5uo 5uo 5up 5up 5up 5uu 5uu 5uu 5uu 5uu 5v2 5v2 606 606 606 606 606 606 606 8ptI was able to sucessfully go through two rounds of bronze and get the rare spin, but of course since bronze has so many players your experience will vary greatly.
While it might be a little slow, cards like dusk mantle and steal can slow down your opponents. Since there are many immodecks in bronze, using cloak to protect your creatures and permanents is a good idea. The dusk mantle allows the possibility to block all damage in a turn, which can be a valuable tool to have. It can also let all the damage pass through, but on average 50% of the attacks to be blocked. Bronze also has a lot of Dimension shield decks, which means you will want to be able to get through the shields. Steal allows you to do that. They also usually have cards like lightning and parallel universe, which can kill your dragon or make a copy of your current dragon.
