Customize a Timber Wolf Mech with the following:

300XL Engine
10 (20) Heat Sinks
4 Jump Jets
STD Internals
12.00 T Ferro-Fiberous Armor

Armor allocation
Head: 9
Right/left arm:24
Right/left leg: 32
Center torso: 32-14
Right/left torso: 32-10

Weapons/Ammo
8 LRM-15 w/1 ton ammo each
With this setup, just lock and fire one string of missiles out to two, fire the next. Keep following that pattern to kill everything in thirty seconds.