Like most bosses, use your surroundings to your advantage. With the MINAC, use the rocks along the end of the map as cover and pick off MINAC until he is defeated. Make sure to utilize a spot where claptraps cannot get to you. Usually, a crevice or on top of another rock since they cannot jump. Oddly, it really does not matter if you die since you will respawn on the map right where you left off so don't sweat it if you are accidentally killed. Once the MINAC is destroyed, INAC will come out, which is like killing any other claptrap so just be sure to kill it before it kills you. See the video below for a good strategy for utilizing the above-referenced strategy. Credit goes to Gam3Junki3z.
Happy Hunting :)