While most class/spec combos will really want engineering, I think enhancement shamans can make a case for skipping it. You already covered most of the gear suggestions I wanted to make; here's a thought on level and gearing:
If you go to 52, you can use the Axe of the Deep Woods, and get the random satchel cape (capable of wrath enchants) and random satchel belt. The Axe may not be worthwhile if you get a lot of extra throughput from using the Living Steel Weapon Chain. In the end, you'll want to check the math on how much you would lose to secondary stat degradation compared to what you would gain from new gear.
Going with the Searingscale Leggings and Bloodshot Greaves will lose you some stats, but you'll gain your 5% bonus from wearing all mail. That may come out even, but net you some extra armor for survivability. Finally, compare the stats and capable enchantments of the Savage Gladiator Chain with your current BoA chest.
My instinct says stay at 51, since that nets you more burst even though overall damage stays the same. But some of the stats differences are worth considering, and tremor totem at 52 is great.
I think that my ironfoe is still better than axe of deep woods imo. the 2 extra attacks is more than double the damage than the axe of deep woods proc and that is only on normal hits.. but 2extra ironfoe hits can also happen on a crit, let us say i crit for 400 white with my ironfoe and it procs on that hit so instead of just 400 damage I will do 400 x3 on that same hit. And it procs quite often. Especially at my lvl I think. I have read that hand of justice proc chance scale on level so I think it is the same with ironfoe and other items with proc on chance, especially the extra hit chance. So being at level 51 also secures that I have the highest possible chance for my hand of justice and ironfoe to proc (not to forget about scaling of other stats, agi/crit/hit/exp stats although hit and exp auto will be higher with 1 more level but I find it cooler/more fun/fair/motivating to be the lower level guy to nuke higher level dudes)
About mail gear and 5% I did the calculations (agility) and my a'atail leggins are simply without any form of competition when it comes to stats, I will still win faar more with them than with full mail and enough that the armor will also not be worth it.. My atalai legs have 41agi 34stam and 14hit!
beside that I have better mail leggings than searingscale (I got searingscale too) but in past when
Dragonstrike Leggings - Item - World of Warcraft where the BiS I made them for my shaman and then dropped LW after and trained the gathering proffesion which were best for 49..So I stil have those, but it still can't beat atalai inclusive bonus and armor.
So it doesn't matter so much if I will equip one more leather or not as it is not a change between bonus and armor but only armor.. therefore I am even thinking about
Arachnid Gloves - Item - World of Warcraft of the monkey as a final bis upgrade (note it now has an extra 12agi and 12sta of the monkey, I saw it as i inspected someone the other day on live realm)
But you also came with some good advise, I am glad you told me about the epic gladiator chest I completely forgot about it, I will have to check it out of course. And about those backs for wotlk enchant is worth considering yeah

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Don't mind that livingsteel, it isn't that good. it is of course, but it is also possible to run behind someone and I still prefer my ribsplitter of the monkey with mongu in offhand.. and from time to time ribs of power with 20agi .. then i tried out wraith scychte with mongu, but I were not impressed, first I thought it would be awesome because it scales 100% from spellpower, and an enhance shaman with a good chunk of agi has quite a lot of sp actually, so my scycthe roughly stole 500 hp from enemy on proc. But not worth it in pvp as it is the half, and it doesn't proc so often I think, maybe 1-1,7 ppm.
A tremor is handy yes.. especially for pvp of course. But without gives me more challenge and that I have to think, predict, and more carefully use interupts, and I rarely die in a single fear anyway, my hp pool isn't so bad. But I didn't duel / meet real 54 twinks yet though I think. So I don't know if i need it yet, but so far it went fine.
Right now my account is frozen so I can't continue twinking. But I will in the future.. If anybody is interested this bracket is fun to play in I think at least. I also know others who began leveling, especially gnomes and I will make one too for this bracket in the future. Of course some will argue that it isn't balanced and bad from the beginning because gnomes can get 81stam trinkets and others can not. But honestly hp doesn't give skills and it also doesn't kill alone.
EDIT: Thank you for critizm, and it is always welcome
EDIT:EDIT: Are you sure
http://www.wowhead.com/item=51993 and
http://www.wowhead.com/item=51977#contained-in-item are obtainable at lvl 52? wowhead says req lvl 55
EDIT:EDIT:EDIT: Maybe it is because I can get it if I get into a LBRS/UBRS random? although it never happened for me but technically it should be as I can choose them manually already as lvl 51. Furthermore I didn't try that much the random dungeon on the purpose of finding out if it would happen and so on.