Halana, Kessig Ranger - I really dislike when there is weird stuff like the partner ability on a card, but this is too good to pass. A 3/4 reach is already good value for 3G and the ability can take over the game. Repeatable removal in green is even more valuable than it would be in other colors.
Reyav, Master Smith - Double strike creatures are usually pretty crappy on their own, so it's not that big of a downside that equipment or auras are a requirement. Only works in one deck, but it's powerful when it works and a good signpost for the Boros equipment/pants deck.
Tuya Bearclaw - The average case is probably a 5/5 when you attack. Lack of trample hurts and she's bad on an empty board, but on the plus side she can become huge and will basically fork your pump spells. Manaplasm works great in my cube and it's a fun card and this is probably easier to trigger consistently. Also great support for the rg pump deck. Gruul has some nice guild cards, but Ghor-Clan Rampager can go.
Kangee, Sky Warden - This is basically a slightly better Serra Angel with a powerful anthem effect tacked on it. That is powerful and I like it more than any of the other skies lords we have. But it's hard to find room for it in Azorius and skies is a deck that doesn't really need that much support to work.
Toggo, Goblin Weaponsmith - Not bad, but I really don't have room for another three drop, it has the odd partner ability and red has plenty of great removal. Most likely won't make the cut.
Feast of Succession - Powerful, but I don't like monarch as an ability. Another good wrath effect in black is something I want and I think monarch can be great here, but not sure yet whether I really want it.
Slaughter the Strong - Completely misread that card at first ('each player chooses any number of creatures with power 4 or less') and thought it was completely useless. But total power? That sounds much better. On the other hand it's a bit weird as it's hard to say where it would actually work well. Pure control decks don't benefit that much from it.
Kangee's Lieutenant - If I don't add Kangee himself this may be worth testing. I always have room in the white 3 cmc section and it's a very decent creature for a skies midrange deck or generally a lot of white midrange decks.
Tormod, the Desecrator - For my taste it's a bit too hard to get any value out of this. You don't cast reanimation and similar spells in black every turn and if you're out of luck it's just a vanilla 4/2. If it works it can be great, but I believe in 50% of games it will just sit around as a 4/2 for 4 doing nothing.
Fall from Favor - Dislike the monarch ability and don't want more pseudo removal in blue, but good card.
Gilt-Leaf Winnower - I wouldn't mind removing Shriekmaw and Bone Shredder eventually as I dislike the non-black clause, but the uneven power/toughness non-elf clause is just as random, so this is not the replacement.
Alhura, Solemn Ritualist - While the spirit tokens help this will often be a bad Relief Captain. You can't even put the counters on a token if you want the full value, which is what I often do when I cast Relief Captain.
I don't like monarch as a mechanic, but I agree that Feast of Succession is a very good card. Only 16 creatures in my cube would survive this (not counting growing creatures, so it's probably more like 20) and if the board gets wiped it's pretty much guaranteed that you draw two cards (three cards total) before your opponent can hope to become the monarch. Which should be enough to keep the board control and after a few turns you should win the game due to overhwelming card advantage. Very tempting, I'd add it immediately if I wouldn't dislike the weird monarch ability that isn't explained on the card at all.
EDIT: Don't think haste or manlands are much of a problem. I have about 7 creatures with haste in my cube and all of them go into aggro decks. How likely is it that your opponent has one of these in his hand after you cast a 6 mana spell with a control deck? Happens in 1 out of 100 games, and then it's something to laugh about. Manlands are good in control decks and you can see them before you play the spell. And of course there are only four of them in my cube, so it's not like you see them often anyway.
Imoti, Celebrant of Bounty has a nice effect, but 3/1 is terrible for a 5 mana creature and it's not like you cast 6+ mana spells every turn, not even in Simic. If it was a 3/4 or at least a 2/4 I'd consider it.
Araumi of the Dead Tide is a nice value card, but nothing I'm looking for in Dimir. For a reanimator combo deck the effect is useless as it's too expensive.
Reyav, Master Smith is a great signpost for the Boros equipment/pants deck and I have room in Boros, so I'll definitely try it.
Kangee, Sky Warden is great, the best skies lord we have so far imo. Will most likely include it, but it's hard to find a cut in Azorius.
I would say you're underestimating how good it is at 1 token, that seems pretty darn good at that point.
From all I could find delve costs are all paid at the same time since it's part of the mana cost, which means delve will not trigger the ability more than once, no matter how many cards you exile. So Gurmag Angler will only ever create one zombie token while being cast, even if you exile 6 cards with delve.
Regarding 'it's pretty darn good with 1 token' - compare Tormod to a card like Talrand's Invocation. If I run a card that doesn't work on its own it either needs to be super easy to trigger it or a single trigger needs to turn it into something that is way better than similar cards that work on their own. Tormod isn't easy to trigger and after a single trigger he's still not better than Talrand's Invocation. What I meant with 'barely good enough' is that what you get when you create a single token is pretty lackluster when you look at how difficult it is to achieve. But I agree that if it was a 4/2 for 4 that gave a 2/2 on etb it would be 'pretty darn good'.
I feel like Tormod the Desecrator could make the cut? One zombie token is good value, and there are many ways to get a whole lot of zombies. So it's a very cool build-around and relatively low-risk.
Looking at my black section, 23 out of 69 cards can make cards leave graveyards (1/3). And other colors have some ways as well, with delve and flashback and such.
No idea which cards you run, but in my cube it's 13/65 (17/77 if you count guild cards). And some of these cards won't always work, most others have prerequisites. Way too hard to get decent value out of Tormod considering it's a vanilla 4/2 for 4. With 1 token it's barely good enough and 2+ won't happen often enough. Easy pass for my cube.
Tuia Bearclaw is a great card, will add her for sure. Even with a 2/1 on the board she's 4/4 and the average case should be at least a 3/2, so she's a 5/5 then. She also works perfectly with the Gruul pump archetype I have. Any pump spell is basically copied since she will benefit from it as well. The small downside is that she's bad when she's alone on the board, but in RG aggro you've lost anyway if that happens for too long.
Merchant Raiders feel like a 4 mana version of Fairgrounds Warden. I'm not a big fan of these cards and while the tap effect is overall stronger than the exile effect (no extra etb trigger, no surprise blocker with instant speed removal) it's not good enough for my blue section.
Prava of the Steel Legion doesn't look that exciting to me. Like Arbor already said, a 2/1 for 2 is much more useful than a 1/4 for 3 and 3 mana per token in green is infinitely better than 4 mana per token in white. The anthem effect is strong, but I doubt this is a good card without a decent amount of other token makers in the deck. I had Intangible Virtue in my cube for quite some time and it was way too narrow, that's why I cut it. On the plus side Prava is more interesting, playable in slightly more decks and white three drops are something I'm always looking for. But I don't think I will try him.
Rograkh, Son of Rohgahh is a funny card, but what do you need to make him good? Trample doesn't matter for creatures with low power, first strike only matters early on. So even if you manage to put a Bonesplitter on him he's not much better than a random two drop on its own. Pass.
Yes, Coastline Marauders looks like a very good card. I had Brazen Wolves in my cube for a while and it was boring, but pretty good. This is only slightly less reliable in the early game (and almost useless as a blocker), but it is insanely powerful in the late(r)game. Not that I needed another 3 cmc aggressive card in red, but it's good enough that I will find room for it.
Oh, damn, I just created a thread the same minute you did. Do I need to call the mods to delete it?
The green legend looks great apart from the odd looking partner clause. Turn almost any creature you cast afterwards into a removal spell for a kicker cost of 2. And a 3/4 reach isn't that bad for 3G either.
The red one certainly isn't underpowered, but I don't think I need a 4R ramp card in red.