Twin Bites flat cooldown reduction is not effective against structures.
The only exception to Dragon FormTwin Bite applying on-hit effects to all affected targets is Tiamat and Ravenous Hydra's passive effect Cleave, as it has an internal cooldown of 0.05 seconds when triggered on different targets. This is a special case to prevent abuse.
Active:Shyvana surrounds herself in flame for 3 seconds, dealing magic damage to nearby enemies each second, increased by 20% against monsters, and gaining bonus movement speed which decays by 15% of its original value each second.
「 Magic Damage Per Second: 20 / 32 / 45 / 57 / 70 (+ 20% bonus AD) 」「 Magic Damage Per Second vs. Monsters: 24 / 38.4 / 54 / 68.8 / 84 (+ 24% bonus AD) 」
「 Maximum Total Damage: 140 / 224 / 315 / 399 / 490 (+ 140% bonus AD) 」「 Maximum Total Damage vs. Monsters: 168 / 268.8 / 378 / 478.8 / 588 (+ 186% bonus AD) 」
Bonus Movement Speed: 30 / 35 / 40 / 45 / 50%
Shyvana's basic attacks extend the duration of Burnout by 1 second, up to a maximum total duration of 7 seconds, and deal 25% of Burnout's damage per second as bonus magic damage to all enemies in its area of effect while it lasts.
Dragon's Descent has an effective duration of 20 seconds when not attacking. If attacking continuously with a 2.5 attack speed, it has an indefinite effective duration. With Sated Devourer only attack speed of 1.67 is needed.
Dragon's Descent has an effective cooldown of 150 / 75 / 50 seconds when not attacking. When permanently attacking at 2.5 attack speed, it has an effective cooldown of about 17.65 / 15.8 / 14.3 seconds. Combined with Sated Devourer, the effective cooldown is reduced to 12.24 / 11.32 / 10.5 seconds.