Ok, the video is fine. But 'fine' can be sort of damning when it comes to Kickstarter, so here are a few pointers I would give you (take them or leave them).
1) It's too po-faced. The opening segment and the voiceover is tough to engage with, because the script is taking the task very seriously and the voiceover is sort of monotone. I've said this in the past and I'll say it again: even if the film you want to make is bleak and brooding, the pitch video needs to have a levity and humour that sells you as filmmakers. After all, people are investing in the process and well as the product. I'd recommend opening with interviews of the brothers rather than the prologue you currently have. I'd also reshoot the interviews and make them feel a bit more upbeat and friendly, as well as less scripted.
2) I think you need to be a bit clearer about what you're asking for, from the off. I was pretty surprised when I realised you were fundraising to shoot a proof of concept to pitch to TV networks/VOD. I think that might put people off because you're laying out a product that there's only a slim chance of them ever seeing. There might be a better way of approaching this but, first off, I think you need to be clearer and bring that explanation earlier in the video. After that, I'd toy with rewording that to try and assure people that they're funding something that will be viewable, in some capacity, in the future.
3) I would scrap the bit about having 'written several episodes'. If I'm going to invest in your show I want to imagine that you have done all the necessary pre-production that can be completed before you receive the budget. And writing a season's worth of scripts is one of those things. Mentioning that you haven't completed the writing for the season instinctively makes me think that you're not ready to be asking for my money.
But above all, make it lighter. People won't sit through a 4 minute video if they feel like you're sermonising. There need to be some joke and some self-deprecation thrown in there: it doesn't have to be One Big Joke, just show people that they're dealing with real guys at the other end of the internet.
But, like I said, the pitch is fine and you have some great resources like the concept art, so demonstrate that it's a serious and viable project.