Aiel

ditch giant growth its useless if you have an infinite combo, way better blossoming defense. put in altar of dementia, this way you dont have to attack as a wincon, sure attacking is good too. but sometimes you cant attack or the enemy can divert damage.
otherwise nice to see someone had the same idea as I did. there are a lot of very expensive tutors you could look into if you want to make the deck more consistent fauna shaman for example.

I would replace redcap with bloodspeaker, gets you your win con. Im not convinced of arsonist and traveler, one Drops rarely are exciting. Champion can be recast and an early threat which makes him nice. maybe replace them with zulaport cutthroat and or bloodartist. butcher ghoul is also nice, it would Trigger haruspex twice unlike traveler who only does once.

really love butcher of the Horde as a Card and what you did with the deck, Im worried it relies too much on him though. I would ditch the auras and replace them with some other creatures you can rely on. quest for the gravelord seems like a good failsave. I will have to look into the Colors to find some good creatures that go well with this.

everything the other two said. but Im gonna be more specific.
-get rid of all ulasht you just dont run enough creatures.
-full playset of managorger, its managorger...
-if you play Genesis Hydra into itself or savageborn Hydra or apocalypse Hydra you basically wasted Genesis Hydra.
you have too many pay X creatures that dont have enough Impact on the battlefield. I would get rid of Genesis Hydra and half the savageborn and apocalypse. hooded Hydra is one of the best hydras in mtg get 4 of those if you want hydras.
this might also let you put ulasht back into the deck.
-drop the 4 larger than life and get 4 colossal might and 4 temur battle rage they both do the Job of larger than life but better since they are instant. and depending on your base creature battle rage is even stronger.
- get rid of Hydra broodmaster
- add mana elfs, Advantages: you can Play them early game to Speed up, late game you can sink their mana into heroes bane or use them to block.
- get druidic satchel it either gives you a blocker or ramps for you or worst case gives you life. I have to admit I just like druidic satchel.
- souls majesty for Card draw. or well anything or carddraw but you should have some way to refuel in case you Need it.
-natures way, one of the best green combat tricks.
- also while youre playing red might as well add mizzium mortars, great early/mid game to get rid of stuff for just two mana, that can give you a nice boardwipe lategame.

KJSJ3 is right this deck wont work consider you start with 6 0mana artifacts and mycosynth golem and you draw every turn a 0mana artifact the earlierst you can play him is turn 5. and you cannot use any of the creatures you have to block cause you need them for synergy means you leave yourself exposed for 5 turns at minimum. hard to make a comeback from that, also like I said 5 turns are the best case... and this only gives you mycosynth he is fairly weak. you still need a game winning card.

my question might sound weird but when archmage ascension has 6 counters do you even draw cards anymore? it says instead of drawing search your library which basically means any effect that gets triggered by drawing a card doesnt get triggered anymore but effects triggered by searching your library are.
also you have 2 archmage ascension(one needs 6 turns where you draw more then one card) but you only have 11 card draw spells... that doesnt sound like its enough. I could be wrong though depends on how it is when you actually play it. it looks like you could need a bit more contagion engines.
also vorel of the hull clade would be good in this deck

shielding plax is illegal with this commander

found an wesome card, dying wish.
wall of blood + dying wish + essence harves/rite of consumption = victory

only idea i have is maybe fists of ironwood, would give a creature trample you can later use for a winning blow with might of the masses to ensure you get through. and the tokens could be used to block before you have the combo out.

awesome combo! really crazy only commons, kudos to you.

if you want to be ahead of your opponent why not bribery and acquire.
thassa makes for a pretty mad commander, easy unblockable and great draw control with the scry.

if you splashed white you could run solitary confinement

you completely misinterpret something here. jace doesn't let your draw 10 cards. the cards are put from the library into the graveyard this doesn't trigger notion thief. but he could still be used to speed up the milling process.

I'm not sure what the rules are but hypothetical if you played a cephalid looter. his ability should give you the card draw and your enemy the discard. as long as notion thief is out there, pretty evil stuff.

great deck, really love the creative use of notion thief, its pretty late where I write from so I'm gonna get back at you with some input when I had some sleep.

i just dont get spreading seas, is it to get rid of non basic lands?

eladamris call is more like an early game, i get what i really need. congregation at dawn strikes me more like, okay i got everything set up, now let the big guys come and handle it card. it would sure work but it doesnt look like the card this deck needs. the only two creatures you really need are knight of new alara and either scrapbasket/transguild courier.

tutoring would be nice, eladamri's call would work perfect with your colors. sadly it blasts the budget.

okay doesnt work for modern but still works as i said. but if you wanna stay modern he's out of the picture anyway
something else that would go great with the deck is austere command.
and if you want to remove anything, ney what you really should remove/replace is wake the reflections, all you get is a 1/1 token for one mana. there are better spells out there. this spell would make sense if you had a way to create far more powerful tokens.
i have no idea what you should replace it with yet, maybe i find something.

your mana curve is completly off. get rid of all garruks and lurking predators
you don't run enough elves for elvish archdruid to be really useful but you could add elvish piper, would boost your archdruid so maybe you get enough mana together for crush of wurms plus you can get slagwurm und elderscale easy into play.
right now you use traproot kami and wurm's tooth to stall time right? but they offer you no synergy
better replace kami with some ramp, maybe another one mana elf(good synergy with archdruid)
put in souls majesty for card draw.
consider cavern of souls, great utility land when you only play a few creature types.(pretty expensive though)
gaea's herald would be a cheaper option.
other nice utility lands: yavimaya hollow(regenerate a creature always nice), oran-rief(+1/+1 counter on creatures), mosswort bridge(possible free crush of wurms)

you dont have to follow all my ideas, just a way i would make the deck work^^