To reproduce:
1. Open attached project;
2. Open "Main" scene and enter Play mode;
3. Click buttons "LoadAsbOne", "LoadAsbCtrl" and "LoadAsbNoCtrl" and see the loading results in the Console.

Note:
LoadAsbOne: loads all assets built in one Asset Bundle;
LoadAsbCtrl: animation and animator built into a common Asset Bundle. Other assets built in a bundle. Prefab Avatar_Theresa_C1_YD_bak's animator controller is not null.
LoadAsbNoCtrl: animation and animator built in a common Asset Bundle. Other assets build in a bundle. Prefab Avatar_Theresa_C1_YD_bak's animator controller is null.

Result: when a prefab in the Asset Bundle has an Animator Controller, loading it from Streaming Assets takes significantly more time:
LoadAsbOne: 187.5 ms
LoadAsbCtrl: 1128.4 ms
LoadAsbNoCtrl: 31.4ms

Reproduced on versions: 5.6.5f1, 2017.1.3f1, 2017.2.1p1, 2017.3.0p1, 2018.1.0b1.