Hi all, I`m curious about what would be the ideal moment to begin the main quest of Hearts of Stone: I have just begun the main storyline quest Battle Preparations, and am at level 32.
I have already finished the game once, so I know what I`m about to get (I`m just playing again to see where other choices lead me). However, I had already finished the game when Hearts of Stone first came out, so I started it after finishing the main storyline.
Can I just do that again, or is there a more adapt moment to start it?

Hearts of Stone (and Blood and Wine) are completely self-contained. The problem with starting them during your main story phase is that you'll be overpowered by the end game. Finish the game and then do the DLC, unless you don't care about being overpowed. In that case, do them when ever you wish.

Great to know, at this point I think I`ll finish the main story and then do the DLCs. Thanks for the advice ;)

Storywise Hearts of Stone could be done before going to the Island of Mists. In my oppinnion one don't neccessarily just OP playing HoS, If you already are at the level when you can complete the HoS quests like level 32'ish, you are already overpowered for the endgame.

So just play the endgame with enemy scaling on, and you'll be set, dificulty wise.

BE ADVISED, atleast these boss fights are "broken" with enemyscaling: Djinn, Olgierd and Imlerith.

Yes, but until you do Blood and Wine you can't get Moreau's enhancements. With the enhancements you also need to upgrade your vineyard in Toussaint and one of the most important is replacing the bed with a muy expensive royal bed. Your headman Barnabas will get it for you.

This is important before fighting Imlerith or Eredin later because your max vitality normally is 100. With Moreau's mutagens your max viitality AFTER sleeping in the royal bed is 1000. Makes killing those big elves a lot easier. Hit Imlerith with the freezing Shockwave and watch his health drop 25% immediately. Then three or four sword strikes will finish him off and you don't have burn his face off as the game is scripted. It makes that arrogant pissant Avalloc'h very nervous and that is gratifying.

Do Hearts of Stone first and then you can declare or dump Yennifer. I have begun to dump her because she is very disagreeable. In order to save Triss you will have to do this before returning to Novigrad to begin saving the mages and the few surviving lesser witches. After that and before you take Uma from the Baron's stables to start the endgame, go find the two knights from Toussaint and start that DLC. Like I said getting the vineyard upgraded will help you survive the Wild Hunt.