What have you ever played L4D? Hell do you even understand the concept of what L4D is trying to do? I am going to go with no for both of those questions. L4D is mainly a coop game and that is where it excels. What you linked is definitely not an improvement on L4D. If anything it is an improvement on Dead Island. The best part is the same people that made Dead Island are making this game and it is roughly the same concept just improved a bit and in a different direction. In other words to answer your question no and analyze a game better if you are going to compare Dying Light to L4D.
both.[spoiler](bill dies in 2, btw)[/spoiler]
yes, survival. i think the inability to go beyond a fixed path even a little bit and the design of infected slowing you down constantly with slug rays/taking 20 hits to go down, and simply making a bunch of choke points is both lazy design and flawed.
it essentially is a lame mod for Counterstrike that was expanded, further modified, and made into an official game, and even runs off of CS files.
this Dying Light is a co-op-able game as well, drop-in drop-out supposedly.