Ryudhyn

You have 13 cards that are cost 5 or higher, which seems very high for an aggro deck. I understand it's not the fastest aggro deck, but if you're planning on winning turn 5 consistently (or even turn 6 or 7), you'll never get out your 7 or 8 drops, and likely not even the 6 drops. You may want to look into that.

Add 4 Akroan Hoplite, Perhaps 2 Assemble the Legion, and perhaps 2 Spear of Heliod

It feels like, with what you're trying to do, you should have a bit more land and some instant land ramp cards as well. Then you can play it like a Draw-Go deck, and if you didn't need to flash in a creature during their turn, you can get some more land so that next turn you can flash even MORE creatures. =D

I think you have too many cards that aren't relentless rats or a thrumming stone. =P

But seriously, it's a good deck.

Yes, that would be a major asset to you.

Comet Storm, Heat Ray (creatures only), and Volcanic Geyser are the ones I know.

Just so you know, Braid of Fire won't be able to help with Fireball or those other X spells. The mana Braid of Fire adds comes in during your upkeep, and then fades when it changes to your draw step, so you can only spend it on instants during your upkeep.

It's much more playable now without those hard-to-play cards. I really like the Gitaxian probes, since they're just blank space basically. The Fireblasts can hurt you if you get more than one in the opening 3 cards, but they're still useable. You might want to consider 2 Thunderous Wrath and 2 Fireblasts, since they're basically the same but with slightly alternate playabilities.
I'm a bit concerned with Pyrostatic Pillar, mostly because I've never used it. I'm still making my mind up on that one.

As for your sideboard, you have 8 cards against lifegain, but I haven't seen many lifegain decks recently for you to be opposing (I may be wrong though). All in all, I'd say it's very playable. Good job. =)

If you add four Tropical Islands in place of your two Islands and two of your Forests, It would add a little bit more ease of land fixing. I don't know if it's worth the cost of them (about 100 each, revised edition), but it might help.

But I really like this deck. Seems to consistently win first couple turns.

For my honest opinion: you have too little land for any sort of reliable mana base. Also, you have 6 cards that require sacrificing artifacts, with 6 artifacts (four of which are lands), so you'll likely not be able to play those, and even if you can, you're screwing your mana base. Also, the 4 fireblasts screw your manabase and the 4 goblin grenades will almost never have a sac outlet. You're kinda screwing yourself over by having too many things that require sac's and not enough things to sac.

Imprint re-triggers every time it comes into play. So if you blink a creature with imprint, the old imprinted thing is gone and you have to imprint something else.

Black Vise is banned in Legacy, so unfortunately this deck is Legacy-illegal. It can be used in Vintage, though.

I know you may be trying to fit it into RW completely, but you have a lot of abilities that don't stack onto each other (First Strike to Double Strike, as well as multiple copies of Vigilance, FS, DS, and Haste). If possible for you, you might want to at least splash a third color, as the point of Slivers is to have as many abilities spread around as you can.

If you're set on RW, however, you might want a couple Thorncaster and Steelform Slivers, as they DO stack upon each other and themselves perfectly.

There should really be a Bump in the Night in this deck. Just for flavor.

Oh, I absolutely know it's a joke. $85,000 for a deck that's illegal is not something someone takes seriously. I was just talking statistics.

Seeing that you need all 7 cards to win on turn one (5 lotuses, 1 Blightsteel, and 1 Lightning Greaves), I got about a 16% success rate (or 1/6 of the time).

Perfect. Now, the only issue I would see with it is your land base. Typically, a speed deck (win in 5- turns) wants 20 lands, but if you play for the mid- or late-game you should have 24 lands or so, or some searchers. Most of your cards seem to be midgame (lots of cost 3, and cost 6 for your finishers), so you may want to find a few more land slots to fill up. Wake the Reflections seems to get out the least amount of creatures per card, so that one might be good to remove and replace with some more lands.

It seems that you want to use Showstopper to deal damage to players (as you say, "Showstopper can kill one opponent"), but that card can only deal damage to creatures. It still may be a viable deck, but you might want to put some thought into that.

Well, one big problem I see is your mana base. You have 12 W producers and 14 U and/or R producers; but you have twice as much red mana in your costs as you do the other two colors. I think you should look into either a more balanced colored deck OR balancing your mana so you have a little more red in there.
Also, along the same vein, with only 20 lands you may have trouble getting to all the cards you want; ESPECIALLY if your plan is, as you say, "assemble the legion into dragonshift". That requires you to stall until you have 5 mana, which with 20 lands will be around turn 8 (which it looks like your deck may have trouble with, since you don't have any removal that can kill a toughness of 5 or higher, except Azorius Charm, which only bounces it for a turn). Then, once you get out an assemble the legion, you'll have a bit of trouble stopping someone from removing it (since it's the first big spell you're playing, they'll probably have a counter to it pretty quickly). THEN, if you can keep it, you have to stall for at least 3 or 4 MORE turns just to bring your Legion to the power it needs to be at.

tl;dr - I think you need a few more lands, and you need more red mana generators.

Your mana curve is really high. You have 10 cards that are cost 5 or higher, 18 that are 4 or higher, and only 13 that are cost 1 or 2 (only two of which are creatures that can block that turn). That means an average starting hand for you will have mostly things that you can't play until the third turn or higher, and what you CAN play will be primarily aggressive and leaving your defenses open. All this gives aggro decks a HUGE advantage over you. Plus, some of the bigger creatures should NOT be in this deck. Your Bloodlord of Vaasgoth is very inefficient by being in a non-vampire deck; almost all of your non-zombie creatures will be severely less important in this deck.

I would suggest reducing the count of your big creatures so that you only have 4-5 cards of cost 5+, and (since your focus is to be running the Gravecrawler combo) you should put in some Transmute cards from the original Dimir. Dizzy Spell can be used to search for Gravecrawler, OR it can be used to stall an aggro deck until you gather your resources. Brainspoil can be used to transmute into Grimgrin or it can be used as a creature killer, whichever you need more.

Overall, I'd say have 4 Gravecrawler, 2-3 Dizzy Spell, 4 Grimgrin, and 1 Brainspoil. The rest of your cards should be lower-cost zombies or zombie-token summoners (Diregraf Ghoul, Vile Rebirth, etc.) to block or pressure, and some good stall cards until you have the mana you need (Mana Leak, Downsize, etc.).

Good luck with the deck! =)