I've personally never been a huge fan of
Host of Thousands outside of Moria Archery (where it's more about getting specific minions out than just getting sheer numbers). The only crappy thing about
Host of Thousands is that you might not have any Orcs in your discard pile at site 4 (or at least, not as many Orcs as you have Hosts in hand). Site 4 is pretty big for Moria -- it's the first site where you're not roaming, and it's entirely possible your opponent isn't yet prepared to see more minions than companions. It sucks having your opponent move to site 4 and having 4 Orcs and 2 Hosts in hand, when you have 0-1 Orcs in your discard pile.
I'd personally switch the Hosts to Moria Scouts. It may even be worth including a
Host of Moria or two just to get some conditions back if you run into a GST or something, but even that's not something I really do in my "standard" Moria setup (or at least, I don't think I do... haven't played basic Moria in ages), so it's really up to the deckbuilder's preference.
I'll echo the thoughts on the
Goblin Flankers. The beautiful thing about Moria is that it's one of those few Shadows that's capable of killing on a single move at any given site. You shouldn't have to use up deck slots on a card that's centered around your opponent double-moving, imo.
Also, I've personally never been much of a
Goblin Backstabber man, but to be fair, I've never really given them a fair chance. Maybe they're awesome. I don't know!
I'll also agree with Ket on Sneaks. Sneaks are great, especially if you can get 1-2 copies of
The Underdeeps of Moria into your deck.
I'm not sure what the meta is like for movie block, but if you need to get rid of Dwarf/Elf cards, then I suppose the Scrabbler and Warrior are good additions. Can't really comment on it for sure, as I don't play movie block (which makes you wonder what authority I feel I have to be posting on a movie block thread, eh?).
So, in summary, I'd recommend this for the Shadow:
-4
Host of Thousands-2
Ancient Chieftain-3
Goblin Backstabber-2
Goblin Flankers+4
Moria Scout+4
Goblin Sneak+2 Underdeeps of Moria
+1
Host of Moria/Guard/Commander/Goblin Swarms/Whatever