I can’t add to anything ultra or others have said about Moreau - he is a purple, stronger version of an already excellent hero (Drake).
But I can say a bit about Lepiota who I have been using successfully against top defences and is imo exceptionally powerful, strategic and fun. It is not just being able to ghost dangerous enemy heroes but also then being able to ghost tiles into the spaces left behind. So she is useful both in preventing bad things happening to you and in then creating the opening you need to get your own specials charged. Her fast speed often means she is charged again before the ghosted hero returns so can keep them in a perpetual ghost lock doing damage all the time (108 per turn for my +9 lepiota) - or move on to another victim. Even in the end game, her special is still useful as a debuff.
Bear in mind that monks (eg bera) can resist her special and that minions seem not to be ghosted even if the hero under them is, also that ghosted heroes can still receive a minion. She is also not a defensive or titan hero. I didn’t experiment with her at 3-70 but I would imagine she is quite viable there - her passive will keep her alive.
At the end of the day it is all about how you like to play but for me she is pretty much my favourite hero right now.