Add something like Krark's Thumb into the mix and the odds are even more in your favor
The reason why I prefer Secret Plans over Rashmi, is Rashmi is a creature
Decks playing Delver of Secrets are at the top of the heap between RUG Delver and U/R Delver, so much so that the vast majority of the Top 8 of this event was Delver variants
So, what we really want to see on warp cards are good abilities triggering when the permanent enters, considering how this mechanic leads us towards playing a certain number of Flicker spells in order to access a way higher quantity of value

0002_MTGTLA_BBTheme: Aang Tutorial Theme Card 8 Plains Aardvark Sloth Razor Rings Path to Redemption Appa, Aang's Companion Sledding Otter-Penguin Aang, Air Nomad Katara, Heroic Healer Momo, Rambunctious Rascal Aang's Defense Sokka, Wolf Coves Protector Tundra Wall Wolf Cove Villager 0008_MTGTLA_BBTheme: Zuko Tutorial Theme Card Dragon Moose Explosive Shot Run Amok Fire Nation's Conquest Komodo Rhino Zuko, Avatar Hunter Zhao, the Seething Flame Iroh, Firebending Instructor Zuko's Offense Fire Nation Soldier 8 Mountain Capital Guard Warship Scout 0001_MTGTLA_BBTheme: Allies Theme Card Kyoshi Warrior Guard Jeong Jeongs Deserters Glider Kids Avatar Enthusiasts Allied Teamwork Aang, the Last Airbender Suki, Kyoshi Warrior Rabaroo Troop Master Piandao Mechanical Glider Path to Redemption Airbending Lesson Thriving Heath 7 Plains 0004_MTGTLA_BBTheme: Waterbending Theme Card Flying Dolphin-Fish Otter-Penguin Katara, Bending Prodigy Sokka, Lateral Strategist Cat-Owl Flexible Waterbender Giant Koi The Terror of Serpent's Pass Watery Grasp Bender's Waterskin Deny Entry Waterbending Lesson Thriving Isle 7 Island 0003_MTGTLA_BBTheme: Spells Theme Card First-Time Flyer Master Pakku Rowdy Snowballers Iguana Parrot Turtle-Seals Geyser Leaper Serpent of the Pass Barrels of Blasting Jelly Abandon Attachments It'll Quench Ya

One easy way to circumvent this weakness is running High Market so you can sacrifice it at instant speed and prevent it from getting exiled