I just saw it as simply worse than Brain Geyser and Stroke of Genius
There are only a handful of ways to remove specific cards from your opponents deck, most of which are known by the slang term capping or surgical-ing. These come from Jester's Cap and Surgical Extraction, though there are a few other cards that are similar
And just in case, since protection is a tricky keyword: The bonuses that Sword of Fire and Ice provide do have synergy protection from a color not only protects against removal, but also lets you bypass blockers from that color
Illustrated by Gabor Szikszai Standard Legal Alchemy Legal Pioneer Legal Historic Legal Modern Legal Brawl Legal Legacy Legal Comp
Otherwise, step on the gas, stop their life gain and go for the win because 4 damage is a lot and the loss can sneak up on players that are not keen on calculating your pump spells and burn
Spells with split second only prevent new spells and activated abilities from going on the stack until those spells resolve, but once the spell with split second resolves, you're free to interact normally with any other spells on the stack