Hey there :).
There's some cards on your deck which are pretty much useless and doesn't fit to the current meta. Like you said, there's a lot of taunts. I'm on Europe, actually Druids / Warlocks and pallys are pretty common on Ranked mode.
Chillwind yeti is a good value card, but has nothing to do with the style of your deck. The original source was designed by Kithros (there was a post about it few weeks ago). Cold blood is good, but it looks more like you tried to create your home made leeroy than anything ^_^ !
What you need right now is actually 1 blade flurry to replace the yeti (clear warlocks imps/murlocs). i would also replace the gnomish inventors by 2 argent squires (you dont always drop your defias and this card can make the tempo against mage + the combo with buff cards is very nice) it's a very good value card.
I don't recommend to keep the gnomish inventors, Kithros explained actually he replace them by harvest golems :). ( http://us.battle.net/hearthstone/en/forum/topic/10357945967?page=4
You'll also find here a description of all "good potential cards" you could add on your deck.
Followed by a video of him playing the deck : http://www.youtube.com/watch?v=QefnCllxkf8
Here's the one i run : http://www.hearthpwn.com/deckbuilder/rogue#33:1;74:1;87:2;128:2;244:1;280:1;286:2;382:2;385:1;386:2;395:1;417:2;434:1;435:2;463:2;471:2;473:2;542:2;627:1;
I just had Sylvanas earlier on and as you can see,it looks the same as you. Your playstyle is much more important than legendaries, sure they help but understanding the matchup you play is also very important :). I lost a lot by doing missplays, raging about not having legendaries before realizing that i wasn't even looking at the timing of other classes (curve and stuff).
Back to my deck I'm testing one Ooze (dealing with weapons,tempo in RvR). Sap is there instead of assassinate (to not trigger Deathrattles "Sylvanas / Tirion ?" + it cost less) 1 also replaced 1 azure drake by 1 Smith, to land it against mage before flamestrike (doesnt die if board is clear "has to be" and give a 7 damage minimum potential next turn) or combo it with bladeflurry ( Deadly poison + this + bladeflurry = 5 damage aoe / 10 damage on the enemy champion "Low cost Pyro").You can also sap it for having the buff.
Hope it helps :) !
PS : Perdition blade for me is only a removal (combo), cant be as good as deadly poison :). In efficiency. About arcane golem,its more or less the card i would recommend if really you want to "low cost leeroy" but i dont think its that good. Sylvanas is really the card you want in first on your deck,since she can save a game if well played.Leeroy needs a lot of set up to be efficient and,for me,its a surprise element, nothing else.with a meta full of taunts ( druids 3567 taunts in hand) leeroy becomes a removal,when sylvanas actually denies this. Having her on the board forces players to not play "big cards", and they will try to remove her at any cost,that's why she has an insane value right now :).