Tacosnape, I really like the playset of Jace. I hope people start to realize soon that he is the single best card printed for control in a long time. I've been running 4 in various Landstill builds (Ugbw and UWr) for ages and I'm never going back to less than 3. But I do have some issues with the list you've posted:

0) I realize that the entire point of Walker is to not run Standstill, but it is still the best draw engine at a U-control decks disposal. Why? Because an early Standstill will either be an Ancestral Recall for 2 mana, or it will slow the game down to draw-land-go, which is just as beneficial. If your opponent is not playing spell and just dropping lands, that means you have more time to drop lands and set yourself up for the lategame. Seeing as how this is a control deck, time to set up is better than card advantage, as your lategame drops will out-class their lower mana drops. The ability to Swords a 1 drop or drop a EE for 1 and then drop Standstill simply outclasses every other draw engine available (except for Jace of course). The only matchup where Standstill is anything short of amazing is against Vial decks like Gobs and Folk (more on that soon).

1) I like the lower mana-curve, but your manabase sacrifices color-consistency for a *slight* increase of resiliency against Wasteland. I say slight because you still run 8 duals and 4 Factories, and will undoubtedly draw 1 in the early game. You run 23 lands, and 6 of them don't tap for blue, making it difficult to cast a T2 Counterspell. In addition, you have 3 EE, 3 Vindicate, and 4 Jace, all of which are color intensive and running basics plus Factories decreases the likelihood of playing those cards early (you know, when your fighting just to stabilize and stay alive). Also, I understand Factory is badass, but you run nothing to take advantage of it. No Standstill, no Crucible, no Humility, no Elspeth. Protecting Jace and being a detergent to little dudes is nice, but the Wasteability of it and the fact that it doesn't tap for colored mana is pretty significant.

2) Understandable. You can't solve every problem preboard and Spell Snare is pretty amazing right now.

3) 4 Plagues says you don't fear Goblins or Dredge. That's it. Those are just about the only matchups where Plague is a significant bomb. Unless you have two out, it's a Thunderstaff against Fish. It only kills a max of 8 dudes without a lord in play (Cursecatcher and Adept), and most Fish builds run 12 lords (LoA, Reerjay, Commander). You only have 4 Swords for cheap, targetted removal, and the rest is either slow (Vindicate, EE) or untargetted (Edict). You'll also be playing it on T4 or later (unless you like to get blow out by Daze/Spell Pierce), and that gives them plenty of time to shit out a few lords or put you in the danger zone (6-7 life or less). Many Fish builds run a few Needles in the board, and Needle on Factory or Jace is pretty shitty. Your draw engine (Visions) conveniently triggers their draw engine (Standstill) and won't net you a single card until T5 at the earliest (unless it eats a Stifle). Basically, Merfolk, one of the most common matchups in Legacy for a variety of reasons, and the premier "anti-blue" deck, straight blows you out barring terrible draws on their part and nut-draws on yours. For this reason most importantly, I suggest (see section 4)...

4) Red is better than Black. But Red AND Black are better than either. Why? Aggro, Blue, and Extirpate. Forsaking Red means you lose out on 2 of the best cards control can run in Legacy: Firespout and Red Blasts. Firespout is simply the best card available to you in the Merfolk, Zoo, Goblins, and other random aggro decks (like DnT, Elves, GW Survival). It's a 3 mana sweeper with easier color requirements. The ease of cast-ability and efficiency of it give it so much power. Even fetching a Volc against one of the aforementioned will change how the opponent plays. Nobody likes to get blown out due to a sweeper, so they'll often use more conservative play, giving you more time to draw gas and additional answers. REB/Pyroblast are amazing for reasons I shouldn't have to explain. In any given metagame, you can reasonably expect 35-40% of the field to be blue. That's a 1 mana Vindicate or Counterspell in 35-40% of your matchups. It gives you a significant boost in the Fish matchup, better game against CB and other U-control like Landstill, and additional cards to side in during the Storm matchup (which is not a great matchup).
The merit of black is questionable depending on metagame. The main reasons to run black are 1) Extirpate (huge), 2) Plague (relavant), 3) Perish (depends on metagame and MD choices), and 4) Vindicate (a solid, but never amazing pick). VVSur's prevalence is enough reason alone to run Extirpate x3, but the rest are arguable, especially with your choice of 3 MD Edicts as an out to Prog making Perish less significant.
I see no reason what so ever that you couldn't drop the Swamp and 1-2 Seas for a few Volcanics to significantly increase your game against both Aggro and Blue decks, while at t. Giving your EE's the ability to hit PWs (which you admit is a major PW for the deck) is significant. In a month (more than likely), Extirpate's value will drop significantly due to lack of VVSur and a predictable rise of both CB-decks and various aggro will make Black even less useful and probably push Green to be a better splash color (KGrip, FS for flyers, Nature's Claim), but that is completely arguable.

Really, Walker is a badass deck, and a blast to play, but there just isn't a U-control deck that can handle VVSur AND Merfolk AND Storm effectively enough (except Deedstill) to warrant play right now. Good VVSur pilots can play around hate pretty well and they know how to avoid Extirpate blowouts and common hate like Needle, Crypt/Relic. The ability for the deck to just slow roll you by hardcasting Vines and running us out of removal/countering it is just too hard to handle. You may win a few games against bad pilots, but anybody worth their salt playing the deck is going to know what your siding in before you scoop up your cards.

If VV (or Survival) gets banned though, this deck could definitely be a contender. The only problem I see is lack of a consistent, fast, and efficient draw engine. Visions is just too slow and is a terrible topdeck. Standstill is terribad against Vial decks. FoF is 4 mana. Jace, The Man Who Wins Games is probably the best engine available, but that puts you in the decision of using him to draw cards or "race" by Fatesealing. We need something to supplement him in the mean time. I have a UWrg list that is reasonably effective against an open meta, but just scoops it up to VVSur. So we'll see where the deck will go come December 20th.