1) The particular point you're mentioning in regards to gear in relation to pure running of 3D content, there are plans to have the minions and contacts provide scaling rewards based on the time you let them run for. Without going into too much detail if you choose to have a contact do something for 24h, upon their return you may receive a bushel of items from a relevant loot table, compared to the players grinding through and focusing on quicker contact actions to boost their XP and Gold gain. We feel this will balance out the problem you're pointing out here but nothing is perfect, and we will be adjusting once it is released.
2) In the end this comes down to individual players. Some like to stop and smell the roses, and others like to speed through for the xp gain at the end. It's not up to us to decide which method the player should play so much as allow players the means to play as they please within the confines of the game rules. This new system will help to appease more varying play styles while still providing cool rewards for players that approach it from those different angles.
3) This is very true, and PvP may see a small decline upon this system launching. We will be monitoring the boards and feedback on these things and we can adjust accordingly. New pvp arenas are in the works for the future, and we can always revisit the matching criteria to favor populated games based on hwo this plays out. Even with the easier access to PvE content a majority of players still really enjoy the PvP in Dark Legends, and I would expect that to continue to be healthy.
4) The current idea is likely to start integrating certain vanities into the world as very rare drops to reduce the crazy requirement of gold for certain outfits. While it's true the prices for gear will begin to drop on the AH as more flood the market, certain items will always be more primo for PvP vs PvE, and priced accordingly by players. There are some other things we can do to reintroduce rarer or different items to keep the economy from flat-lining. Very valid concern.