I feel you should bring the mountains down to 1, maybe 2 (especially with the BoP). I think the Emissary is a very good choice, but with Dungrove Elder and Predator Ooze, you can run very few mountains while still potentially activating Daybreak Ranger.
I also agree with the other poster that 4 Oozes is a better idea. The card's really good.
One thing I noticed with all of your decks: I think you need about 1-2 more lands. I'll admit that I haven't played in a long time, but your landbases just look like they're begging for mana screws.
I'm torn between Marauder and Ordeal though. Normally I'd say go with the creature, but we don't have that much devotion to black, and more blue permanents are better for Master of Waves and Thassa (though it doesn't look like we'll ever get enough to trigger Thassa).
With us being three colors, and looking like we're going to be somewhat evenly split between the colors, I'd rather take the Unknown Shores fixing. We actually have a fair number of playables, and Crackling Triton isn't overly exciting to me.
We're gonna end up BUr or BRu, probably split pretty evenly between red/blue. Our mana base won't be great... but I think we'll do okay-ish. Glad that we picked up Burnished Hart.
I like Aqueous Form, but it doesn't look like we have any creatures that work well with it, and we're stretching for consistent playables. Omenspeaker sounds good to me.
Agreed on Swan Song, pretty sure the card was designed with constructed in mind.
Switching to black looks like it was a good idea though, Pharika's Cure is pretty solid. Hopefully we aren't cut too hard in pack 3.
Signaling kinda gets confusing for me though, so I'm willing to defer to Phyrre and go with Lash. Both Lash and the Emissary are splashable, but I feel that we're in a stronger position to splash Red than black atm, even with Lash.
(Is colossus not worth taking? I have to admit, I don't quite have a feel for the tempo of this format.)
Fate Foretold isn't bad, but I really don't want multiples. Shredding Winds is a nice sideboard card, but honestly we're almost as much in red as we are green, and Rage of Purphoros is definitely the better card.
Also haven't really seen any black in these last few packs.
Warrior's Lesson goes quite well with Agent of Horizons, but still, I think I agree with Phyrre that it isn't really justifyable without heroes. Coastline Chimera isn't a bad card.
For me, it's between Agent of Horizons and Cutthroat Maneuver. Cutthroat Maneuver is good if we get a few good heroic guys, but probably isn't worth running if we don't. Agent is good if we switch to green, and is reasonably splashable even if we stay UB.
I think I'd rather take Agent of Horizons and leave us open to switching to green. Nothing in this pack is exciting.
Scholar is probably the strongest card in the pack, and might not be a bad idea to take in case white opens up.
I'm leaning towards Returned Phalanx, though I wouldn't mind Burnished Hart. Early defenders are kinda needed against Heroic/aggro decks, but we also aren't totally sure yet that black is open.