Re: Miracles
Postboard I am more reluctant to Stifle a Miracle trigger, because it puts you down a card and the games tend to go very long where your opponent is likely to find a way to Brainstorm it back and/or just get to 6 mana and hardcast it.
A more useful application for Stifle in g2/3 against Miracle is to counter a Snapcaster trigger, also remember you can Stifle the Portent draw on upkeep just to 1-for-1 the opponent. (EDIT: Miracles players also often use EE as an answer for Nimble Mongoose)
Since the Divining Top days I have fewer Orb to board in so I end up keeping some bolts in order to have outs to a resolved Mentor
In my experience quite a few Miracles players are trying Azcanta now, which means that Wasteland becomes much more useful than it was in the past (where it was still fine just to pressure your opponent's mana because they were unlikely to draw only basics).

Using my list
50 Stock
4 Tarmo
2 Seal of Fire
2 Snare
1 Pierce
1 Preordain

1 Loam
1 Barbarian Ring
2 Pyroblast
1 Red Blast
1 Winter Orb
2 Grudge
2 TNN
2 Surgical
1 Honden of Infinite Rage
1 Pierce
1 Forked Bolt

-4 Tarmogoyf
-2 Seal of Fire
-4 Delver of Secrets
-2 Bolt

+2 TNN
+3 Red Blast
+1 Winter Orb
+1 Loam
+1 Barbarian Ring
+1 Pierce
+2 Surgical Extraction
+1 Honden

This is what I am on at the moment
Not 100% sure about the 2nd Surgical

Re: Dack Fayden
a 3 mana PW is something that I would be interested in a few matchups, but it needs to be something that is generically threatening on its own and I don't think Dack does this well enough. I have thought about Domri Rade or the UGX Nissa but the problem with these two is that in matchups where a PW would be good you are often boarding some number of your creatures out (and therefore it's too hard to get an advantage from these).