That was my experience with Thought Scour too. It was mediocre at digging (no card selection) and mediocre at filling the yard. It's does a little of both in between. I prefer
Preordain. JBlinder has great results with Thought Scour though! Maybe he can add some insight to how and when he uses it.
Burning Wish finds answers to permanent hate in game 1. It's amazing in prison matchups. Force of Will answers the hate before it lands. Some run Chain of Vapors main. In UWR MentalMisstep runs an ETutor package with 1 Seal of Cleansing and 1 Seal of Removal main.
Nice. I'm leaning towards switching to
Pulverize just for the tempo it has over other tools like
By Force and
Shenanigans.
Burning Wish is amazing in prison and control matchups. In racing matches (combo, Burn, UR Delver), Wish can be slow and clunky. Jblinder and I both started at 4 and cut back to 3. He runs a 4th in the SB. UWR also has ETutor to find answers, RUG doesn't, so the 4th Wish is probably stronger in RUG.
Grapeshot requires a low storm count too. Wish -> Grapeshot -> escape Grapeshot -> ...
Once you have storm 6 and a bunch of cards in grave (2-3 Brain Freezes is enough), that's already enough to win. Escape LED -> Escape LED -> crack for RRRRRR -> escape Burning Wish -> Grapeshot -> escape Grapeshot (21 copies)
Grapeshot has additional utility before the combo turn (killing Thalia and other hatebears) so it's more efficient use of Wishboard space.
Some of the lists I linked on the previous page splash black for discard. Check them out.
Thoughtseize is good. The main drawback is having a less stable manabase. They're usually 4 colors, splashing green or white for SB answers Grixis doesn't have. Grixis on its own lacks Silence/Veil effects and answers to enchantments.