Rumble vs Darius Top Matchup
Rumble Top wins 47.3% of 869 Low Elo games against Darius Top, -0.7 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
How to play as Rumble
Poke with Flamespitter(Q) and Electro Harpoon(E) from outside Apprehend(E) range; Darius has a harder time answering if his pull misses.
Before an all-in, manage Heat so you can fit both Harpoon(E) charges and Flamespitter(Q) before Overheat; the matchup guide recommends weaving those spells into the fight.
Rumble's Flamespitter(Q) and Electro Harpoon(E) can trade from range, while Darius needs Apprehend(E) to pull him into a more dangerous close fight.
How to play as Darius
Hold Apprehend(E) for when Rumble steps into range or commits; if it misses, he can answer with Q and E poke.
Sources
These notes come from r/Rumblemains, checked against the champions' abilities.