*Axebane Guardian + Walls: Lets me hardcast Realm Razer and Sire of Stagnation.
*Wall of Mulch + Wall of Omens: Lets me dig for combo pieces.
*Worldly Tutor: Grabs combo pieces.
*Doorkeeper + Hedron Crab: Mill.
*Ravenous Baloth: sac outlet for Realm Razer. Efficient 4-drop that can buy me time with life gain.
*Reclaim: Lets me recur important things, like a piece that got killed, or go for a second Razer.
I mean, yes, it works, but there are many 2-card creature combos that you can do with 2 6-drops. I guess it could be fun. But your deck doesn't do much if you don't draw the combo pieces, and you can't actually cast either combo piece without mana from Axebane Guardian/Sylvan Caryatid. That part concerns me. Your deck needs to draw a whole lot of pieces in the right order to work, and if your walls are killed by removal then you can't cast either of your bombs at all. When your opponents figure that out, they will prioritize killing your mana walls to shut you down.
I think that means you want more draw fixing. Not just cantrips (Wall of Blossoms) that draw you a random card, but cards like Ponder or more Worldly Tutor to help you draw specific cards. That way you can see cards you need more often.
Also, notice that you don't have to play all 5 colors to do this combo. Sire of Stagnation + Parallax Tide works in just 2 colors and doesn't need a sacrifice outlet. With Sire out, you exile 5 lands with Tide. They probably can't cast much on their turn. On your upkeep it dies to fading, returning 5 lands, milling them 10 and drawing you 10 cards. You'll probably find another Parallax Tide (or draw spells) in those next 10 cards, so you can drop another one on your main phase exiling their lands again (so they can't cast anything on their turn again), effectively locking them out and burying them in card advantage.
Having only Axebane Guardian and Sylvan Caryatid as color fixers can make it very hard to obtain the colors you need to cast your two key creatures. Creatures die after all, and hexproof is no failsafe against that. I think, a full set of Chromatic Lanterns would address this nicely, since even a single copy both fixes your colors entirely and ramps you a bit. I'd play it instead of the Doorkeepers, which don't seem to contribute much. I get that it's an early wall with a mill ability, but you're trying for a few big mill attacks, instead of repeated smaller mills.
I would run a fourth copy of Sire of Stagnation since it is one of your key pieces, and cummulative in multiples.
Another superb defender to go along your card drawing walls is Carven Caryatid.
A copy of two of Oboro, Palace in the Clouds could assure that you have a land drop every turn to trigger your Crabs' landfall. And it does so without any costs at all (it can tap for the one mana needed to bounce it, then you just replay it). Do this whenever you have no land to play during your turn.
I think, Dread Return would fit well into the deck, as a revival mechanism for your key pieces, that can also serve as a means to get rid of a Realm Razer without costing mana (maybe even to get back another one, just to flicker all lands and get all the triggers), and reviving a card draw creature isn't that bad either.