So many people say it's no good, but it's consistently an objectively good card in this deck, and honestly I feel my results justify it-- I rarely, if ever, lose once it hits the board. It lets me attack and block if need be, it lets me sac Mausoleum Wanderer for higher value, it stops Liliana from killing my shit, it stops Languish from killing Avacyn. It gives an enhanced clock on my opponent's life, which gives them less time to fix their own board state and do damage to me.
It's an excellent finisher, overall-- drop it when you have no other creatures to play and have enough mana to throw a counter/unsubstantiate, and wreck faces. Being able to go from having 1 life and my opponent having 29 and still killing them means it's a stellar card for making comebacks. Maybe side it out against decks that run extremely high power/toughness flyers.
Ongoing Investigation has been more of an experimental card for us-- and it does pretty well, actually! Since you're almost always attacking unblocked, you rack up lots of clues to sac with leftover mana. On the other hand, it's the card I ended up siding out the most, too. But think of it this way-- it's 2 mana for a source of card draw that's nearly limitless, while Anticipate only gives you one card, Fortune's Favor and Epiphany at the Drownyard are HUGE gambles, and Pore Over the Pages costs too much to be worth it. As far as I see it, Ongoing Investigation is the most solid card for card draw for Spirits, because it's underestimated. No one's going to counter it, thinking it's a threat-- but when you realize they can't stop me from sacrificing clues to draw cards, it feels totally worth it.
You're right though, six enchantments that don't directly affect the board is a lot-- that's why they were frequently my first choices to sideboard out. It's nice for it to be an easy decision, though-- but I think it's a good idea to keep Always Watching in, if possible.
Think of it this way, as far as AW goes:
Turn 1: Land -> Mausoleum Wanderer
Turn 2: Land, attack for 1, or 2 if you cast a Selfless Spirit. If not Selfless Spirit, cast Rattlechains at end of opponent turn
Turn 3: Land, attack for 3, cast Spell Queller, Rattlechains, Nebelgast Herald, or Selfless Spirit at end of opponent turn (Selfless only if Rattlechains comes down)
Turn 4: Land if you have it, Cast Always Watching, attack for 8 with flying and vigilance
Turn 5: Land if you have it, attack for 8. Cast a Spirit or two, Avacyn, or sac a Spirit to cast Elder Deep-Fiend on opponent turn.
Turn 6: Attack for 11 if you cast a Spirit; 14 if you cast two; 13 if you cast Avacyn, or 10 if you cast Deep-Fiend.
Of course, it never works out that perfectly, but even if you are attacking for 5-8 every turn with blocking potential with just 2-3 spirits and casting counters for the rest of the game, you're WAY better off than doing 3-5 damage and having to have them be tapped.
Always Watching also gets Spell Queller out of burn damage range, too, Exquisite Firecraft aside. With two, it's safe from Languish and Grasp of Darkness.
