It's all what you're comfortable with. I don't find the additional potential "failure points" to be a deal at all. It's honestly a fairly specious argument in the first place. No static hose is going to be any more prone to failure than any other, and as long as you have some semblance of situational awareness when you build your unit, bubble checks, etc., no hose failure should be a surprise. Catastrophic hose failures are so rare that removing 2 hoses in an effort to remove that "failure point" isn't worth losing the MAV in my mind. Minimizing risk and minimizing risk at the expense of utility are not the same thing.
I could literally run my Pelagian with one hose coming from the dil side to the ADV, one from the O2 side to the needle block/mav, and the hose that goes from the needle block into the head. Of course I have to find wing and suit inflation from somewhere else, BOV feed from somewhere else, I won't know how much gas I have, but sure as hell I've minimized "failure points" on the rebreather side of the equation. One hose coming from each first stage is about as failure proof as it gets. Of course I still need wing gas, I still need suit gas, I still need BOV feed, and I still need to know how much gas I have. So it's not like I can really remove them, I'm just relocating them. So, if you've already got n+1 points of failure, adding a couple "extra" like you'd get with a MAV isn't really increasing the risk substantially, but the utility of having it more that outweighs the risk in my mind.
Again, it's all a choice you have to make. If you're comfortable diving without a MAV, or comfortable diving without an ADV, and you can adequately control your unit without one or the other, drive on. For many many dives you may not need the additional utility of it, in which case you're not really losing out by missing one.