I have done moathouse, killed Lareth, done some quests in Nulb then, even visited Temple for a couple of times. But it is still no chest spawned. If it is a known problem advice would be a great help.
Have you been asking the blacksmith for something different? You need to at least accept the Welkwood Bog quest from Captain Renton before going back to the blacksmith and again asking for something different When you have accepted the orc annihilation quest from the village elder you will see that the blacksmith's chest will have spawned by the time you get back to his anvil.
I was under the impression that the chest Brother Smyth offers spawns only if you have a Rogue of level 4 or higher, and it not related to the "something different" quest line at all. It was there long before that Mod, I think it is Vanilla. Do you have a 4th level Rogue in the party? Note: I don't play the Evil Alignment games, so it could be a different trigger, but I am certain it was there before Welkwood Bog.
The chest being there predates Welkwood, but I think in 6.0 when the book for AoH was added the conditions to trigger it changed. I'm not sure it was vanilla though, it feels like a Livonya mod to me. (She really loved those rogues!!)
You do NOT need to have a rogue in your party to trigger the chest. Just get the quest for WB from Captain Renton and then the Orc mission of annihilation from the Elder Kentar Nevits. Then the chest should show up. Remember you need to ask Brother Smythe for "something different".
Actually chest spawned after I got rogue level 3 (he is multiclass so a bit late) AND I have returned from Hickory Branch, killed orc lord. (I did welkwood bog before) No idea with what it is related, last time chest spawned straight after party returned from Moathouse.
The chest has been around since v4, but it's only involved Arena of Heroes since v6. If you play standard, the chest behaves like it did traditionally. If you play NC, the chest behaves according to the NC delivery system schedule. They're not that different (both occur around generally story state 3), but the standard chest obviously doesn't have any of the contact requirements that the NC one does.