any thing below 400 dollars should be considered dead
How wrong can you be... Even if Bitcoin falls back to $1 it can't be considered the end of Bitcoin. Bitcoin comes to an end if all nodes and miners just shut down everything. That's when Bitcoin is dead, and nothing else.
because i remember bitcoin failing to break this barrier for some time
In every market there are certain stagnant periods where the price can't seem to move through certain levels, Bitcoin is definitely not an exception. It's all about supply and demand. At that point there was simply more supply than actual demand, and thus the market stays where it is. No big deal.
and am sure if prices were to go that low some mysterious altcoin might be double its value
That would be a normal market reaction. People move their money to places that at that time offer a better perspective.