@jimtosetti Is Preordain #3 better than a Ponder? Where are you on Mission Briefing after a few leagues? Thoughts on Spell Piece to combat PWs and adding more grudges main?
Ponder can be good provided you get some sequence of cards that can be effective in that particular game. It can be a gamble in the early game because you might not know what you need to win yet. Preordain is consistent at finding lands and the Oath of Druids. Ponder is better in decks that use more fetch lands because you can shuffle the extra cards away. Ponder is also better in more dedicated combo decks.
As far as Mission Briefing and a few leagues goes, its more like Mission Briefing after hundreds of leagues. Mission Briefing has a similar function to Yawgmoth's Will. It is harder to cast when there are more sphere effects in the meta.
I started to test Daze to combat Planeswalkers and counter magic, but my experience is that you still lose to turn one Karn when they are on the play. I have some ideas to test when we can use the Modern Horizons cards the might help Oath in tough situations.
Ancient Grudge is very good against artifact based decks and very poor against Xerox decks. You can probably go two ways with the deck. A general strategy for all matches game one, or a main deck that is focused towards particular matches that sides into the other matches in a strong way. However, players have been successful in relevant numbers using multiple main deck Ancient Grudges.
My experience with Spell Pierce has never been good with this deck, but that was when Xerox was a major competitor. I've thought about trying out one Spell Pierce, so maybe I will try it tonight.
I know that myself and many other people are becoming very unenthused with losing to turn one Karn. At this point it highly probably we are making donations to WOTC when we join leagues.
If I figure out anything significant with the Modern Horizons cards I will post the deck lists and card discussion here. My theory with Magic is to test anything that enters you mind as a good idea. You will never find out if they are good ideas if you never test them. My Twitch account name is the same as here, jimtosetti. I play Oath fairly often. Feel free to come deck build with us there. I'm on most days starting anywhere from 5pm -7pm central time.