The fact she's vulnerable to spot removal isn't that big an issue, since her ability is most relevant against Bant/Naya who run little to no maindeck removal. What is an issue is that, while Linvala stops Dauntless Escort, she also gets wiped when you cast the DoJ that you're preventing the Escort from stuffing. Pithing Needle does the same thing and doesn't come with a body... but it also doesn't come with a body, you know? *shrug*
Grixis plays differently in that it uses a lot of spot removal instead of a few board sweepers but otherwise it operates as your "usual" control deck, regardless of Cruel Ultimatum's presence. That's not the case with Brilliant Ultimatum. You build around that card. It's closer to Polymorph than it is the other control decks of the current format and, personally, I just don't want to play that.
Not to veer too far off-topic but I'd never be unhappy to run Spawning Breath. It's not exactly Staggershock or Flame Slash but there's plenty of 1-toughness thingies to ping off with it while getting a "bonus token" at the same time. Most of the levelers start off at 1 Toughness, so it's great at putting you way ahead on tempo early and it can still answer some evasive creatures (Gloomhunter, Cadaver Imp, the good Invoker) at any time.
Nest Invader is pretty cool too. Sure, bears aren't terribly impressive in RoE Limited, but creatures of 1-2 CMC can still get in some early damage if they don't put down a T2 wall. It's not like it's only a bear anyway but Tahn's copypasta job pretty much covers that.
I do believe most Polymorph decks run white in some capacity. Many run DoJ and a few also have Path to Exile, in addition to opening up the remote possibility of hardcasting Iona.
If you're siding Meddling Mage, you probably shouldn't be naming anything but Polymorph especially if you don't already have an "answer" card in your hand. Even if you do, your DoJ is no longer killing your own Mage (because they must bounce it to Polymorph) or they need an unlikely second bounce spell to answer your O-Ring.
Sarkhan would've at least turned it into a 5/5 Dragon that doesn't even get any benefit from Hedron Matrix. Gideon wins that round but it's not like Sarkhan doesn't do anything at all.
Lavafume is rather unimpressive as Invokers go. I'm more a fan of Soulsurge when it comes to spawn. That 1-toughness is a bummer but it's a real force against non-B/R decks. Neither are "great" and the Invoker is probably better considering we're looking at heavy mana generation, though.
I'm a big fan of Prism. It's colorless and cantrips, so I personally play it pretty much regardless of the deck, and it can really let us splash otherwise good off-color cards later (see: blue second pack of the first RoE forum draft). Guard Duty is potentially such a card for what this deck is shaping up to be... but the fixing needs to be there first anyway. *shrug*
I also like Wall as a speculative pick, and then Summons... Not really the right type of deck for that card? We might as well just wait to see if we can pick up another Eldrazi or two, Pelakka Wurm, or whatever.
I'm voting Prism but fully expect the Invoker to win. *click* EDIT: I feel lonely. Two people even voted for Wall so far.
I also keep my MD deprive post-board because it can clip bloodwitches, SGCs, and Broodmates.
See, that's why I like having a copy of two or that card in these decks but everyone else is always like "oh well I don't need to counter creatures EVER only spells yo!" Playing black splash (Esper variant), I found myself frequently annoyed at having to keep a third mana source open and decided Deprive was better than Cancel when you're only running one or two total as catch-all answer cards.
I don't think Baneslayer should be "replaced" with those cards, since it can very well be used alongside four Path and extra Planeswalkers (if you're not running Chalice and its X-spell buddies), it's simply a question of whether or not it's worth running. Maybe you can do some games with both to decide, personally I really like the 2-of BSA in my deck. While not great against Jund, it's an extremely effective roadblock against all the aggro decks out there running little to no MD removal. It's still as much a win-con as ever if it goes unanswered and it's very similar to Gideon anyway in terms of allowing you to stabilize mid-game.
World Queller is not a terrible idea but Pithing Needle is an extremely versatile card (not just for Planeswalkers!) and there's a massive difference in mana cost. Couldn't hurt to try it, though, and GG if you start to wipe lands on a board clear of PWs.
Outlander indeed... What you have to watch out for against Jund anyway is them SBing in more green to avoid the black/red hate.
I wouldn't bother with SotSW. Deathmark has lost favor with some Jund players, opting for Doom Blade because Instant speed is so relevant (RDW, Conscription) right now, but why even take the risk? It's both slower and more narrow than SoJI, which you can also use in control mirrors to great success.
Boros Bushwhacker? Ravnica is a lot further removed from Zendikar than Zendikar is from Scars.
Nest Invader is pretty cool too. Sure, bears aren't terribly impressive in RoE Limited, but creatures of 1-2 CMC can still get in some early damage if they don't put down a T2 wall. It's not like it's only a bear anyway but Tahn's copypasta job pretty much covers that.
If you're siding Meddling Mage, you probably shouldn't be naming anything but Polymorph especially if you don't already have an "answer" card in your hand. Even if you do, your DoJ is no longer killing your own Mage (because they must bounce it to Polymorph) or they need an unlikely second bounce spell to answer your O-Ring.
I'm a big fan of Prism. It's colorless and cantrips, so I personally play it pretty much regardless of the deck, and it can really let us splash otherwise good off-color cards later (see: blue second pack of the first RoE forum draft). Guard Duty is potentially such a card for what this deck is shaping up to be... but the fixing needs to be there first anyway. *shrug*
I also like Wall as a speculative pick, and then Summons... Not really the right type of deck for that card? We might as well just wait to see if we can pick up another Eldrazi or two, Pelakka Wurm, or whatever.
I'm voting Prism but fully expect the Invoker to win. *click* EDIT: I feel lonely. Two people even voted for Wall so far.
See, that's why I like having a copy of two or that card in these decks but everyone else is always like "oh well I don't need to counter creatures EVER only spells yo!" Playing black splash (Esper variant), I found myself frequently annoyed at having to keep a third mana source open and decided Deprive was better than Cancel when you're only running one or two total as catch-all answer cards.
Questionable call, Hank. AFAIK, most Jund players side out Thrinax against control these days anyway because it can't swing past Wall of Omens.
Outlander indeed... What you have to watch out for against Jund anyway is them SBing in more green to avoid the black/red hate.