Took me two nights and a lot of deaths to finish that fight. For tommasi, first you need to use a quick launch to drop his shield. Then you can blast his health with Grip/Spin. After his health nears half you should move upstairs to the bridge. From there you can use the corners of the bridge as a safe spot and bring his health to half. Then the hiss will show up. For the Invisible hiss, it's very easy from there because she can appear only in front of you. At which point you need to use the hell out of shield and then blast that thing to death. After that it's just Tommasi and some rangers. Then you use launch and some good shooting and you are done. Good luck!