I had trouble at first. I have a poorly planned Guardian and get my butt handed to me often and this boss seemed impossible. After reading some suggestions here it ended up being as easy as the emperor.
Go in and run around it like crazy slashing/shooting at will. When it stops following you and charging its lasers get to its side (NOT UNDERNEATH!!!). After it discharges (my companion was unharmed) stay at the side and it will not move, hit it like crazy. If you don't get it done before it moves again repeat the process above. Again, don't hide underneath, be at the side! After the second discharge you should be able to finish it off easily.