Brief trip report:
Climbed with MikeSash. Started at 4:25am from Baxter Pass T/H. Geared up at the base of the NE couloir around 10am (were dragging a** from post-holing). The lower part was deep snow (was sinking to my knees as I was breaking trail), then it got better higher up. Encountered some rock fall, which made us climb faster. Topped out in about 1 hour and a half (exit of the NE couloir is at 12,900'). Summited by 12:05pm. Rested up there for 40min. Back to the T/H by 4:24pm (12 hrs car-to-car). Cheese burger, fries and a coke at the Mt. Whitney Restaurant in Lone Pine afterwards.
More info about climbing Diamond Peak here.