...turning back to impulse (so i'm not playing phids), thirst are quite superior than phids in those pairings were phid was a dead card (random aggro, goblins, landstill, fish...) this decks are quite popular in my metagame... but phid is still so good againts control or combo...
I haven't test it very much but I think that thirst can be a fine substitute of phid while you don't have to tap in your turn and is quite faster tan phid in the early game...
If you're playing the same kind of deck Mr. vd Hoeven did in Eindhoven, you should NEVER bother about cutting TFK's, they are simply too good to cut.
Basicly, this leaves you with one choice: cut Impulse or Ophidian. I would stick with the Ophidians. This deck runs over random aggro, goblins and landstill, especially after boarding (oath pwns them). I tested a bit against fish and it also doesn't look that problematic. Even with 4 'dead' cards (I don't think Ophidian is dead in aggro matchups) you win easily, the 4 ophidians don't make you lose.
The ophidians really shine in control matchups for obvious reasons. Another reason why they are really good is the fact that they make sb'ing a lot harder for you opponent because they have to handle both creatures, artifacts and a counter war.
I think the Impulses aren't a good choice. Turn 1 is usually filled with playing a mana leak / powder keg / chalice of the void. The second turn is about playing mana leak / mana drain / powder keg / some random bomb. You just don't have the time to play an Impulse, you got better things to do.
Good luck with the deck
