So basicly playing a game and someone was running Gandalf and Nori, played dwarf from the top card via gandalfs effect, does nori's effect trigger

Was also thinking this about cards like rumil, the basic question is i know gandalf can play the card "as though it was in your hand" but does this mean effects trigger "as if the card was in your hand" or is it not in your hand for the purposes of things triggering

I think Nori's effect will trigger. Gandalf plays the top card from your deck "as if it were in your hand," so a Response like Nori's, or Rumil's which can be triggered when the card is played "from your hand," should be legal to trigger.

An analogous scenario is enemies who are "considered to be engaged" with the first player, but remain in the staging area. They still behave as if they were engaged, and attack you and can be attacked, and they suffer from effects like Tactics Aragorn's -1 defense to each enemy engaged with you. (although as an aside and separate issue, they don't trigger a response like Sam's response when they become engaged with you, as it seems that "engaging" a player entails physically moving the card into the player's play area, but "considered to be engaged with the player" behaves differently).