Are there philosophies or philosophers that argue consciousness in the brain arise due to a superposition of the different patterns of electrical activity just before they decohere into the different classical worlds?
I don't have an answer to the literal questions, just some observations about why such an approach may not make much sense.
Despite some old unproven speculations about microtubules in the neurons behaving coherently in a quantum way and influencing mind processes, there's probably not much difference, from the point of view of "quantumness" (or amount of "coherence"), between a classical computer and a human brain. So why evoke quantum to explain consciousness?
(BTW, I'm not saying the human brain works like a, classical or otherwise, computer)
Whether we are physicalist or Cartesian about minds, it's safe to assume that consciousness of an individual supervenes at each moment on certain neurological configurations in her brain.
So, before even mentioning mind, consciousness, and all that stuff, we should rather make a step back and answer the simple question: what's a brain?
Despite the apparence, this is not much different from the question: what's a cat? (or a chair, or a tree). David Wallace [1.] remarks (I'm not quoting literally, and I hope not to have misunderstood the point) that in the Schroedinger cat experiment, just before opening the box, there is no cat in a superposition of states of being alive and being dead; rather, the state of the system is a superposition of two states which instantiate, respectively, a live cat and a dead cat. So, there are two cats in that system: one live cat, instantiated by a certain component of the state vector, and one dead cat, instantiated by a different component of the state vector. This is because what we call a "cat" (or any other object) is (a piece of reality that is approximately isomorphic to) a certain structure that we can read from the formalism: in this case a certain individual component of the state vector [plus probably various mathematical bells and whistles distinguishing it, such as a pointer basis, cause a vector of an abstract Hilbert space just by itself doesn't say much...]. A supersposition of such structures, we wouldn't call a cat... that's just not what a cat is.
The same goes for brains: at no moment one brain is in a superposition of having a certain configuration and a different configuration. There's just a state vector which is the sum of two components each instantiating a brain in its own different configuration. In particular, at no moment one brain is in a superposition of configurations that are supervened on by different mental states. So, in this sense, invoking MWI to explain consciousness may be moot.
[1.] David Wallace, The emergent multiverse. Quantum theory according to the Everett interpretation (2012)