The universal dilemma of the Infiltrator was that few decks that played it wanted to tap out to get him there, but sticking him on the board was so devastating that most opponents would consider themselves fortunate to spend that window of opportunity making him go away as trying to race him with a traditional three- or four-drop was pure folly and playing your own blocker, including your own Shadowmage or something a little bulkier risked a removal spell that would lead into a downward spiral of card disadvantage
No, manifest dread does not include milling
Shroud is a protection that is a double-edge sword, but because this card gives it to all creature until you upkeep, youre using that other edge against your opponents
Thought Scour puts a random card into your hand, Opt lets you choose a known card or the mystery box, Sleight of Hand is the same two-card choice with an open mystery box, and Serum Visions lets you keep both or neither of the two cards you see
Thank you for reading, and keep improving your mana bases