I would suggest having a Bonding Knife on your Farsight team and a large number of Drones to take hits. You should also include a Failsafe Detonator to allow you to escape close combat safely. If you have 2 or so Devilfish for cover then Gun Drones may be fine but Shield Drones are preferable if you have the points.
Remember to also try and keep the team fairly unified in purpose, for example, a constant load out of Missile Pod, Plasma Rifle,
HW Multi Tracker and either a flamer or a Fusion Blaster. You could even have a mix of Flamers and Fusion Blaster as a few of each should be enough for most tasks. Target Locks should be good on a few members, preferably on all of the members toting Flamers
or Fusion blasters if you have a mix, or just take a few if you don't. (to allow split firing on transports and such for efficiency)
I would put an Airbursting Fragmentation Projector on a suit. (with a Target Lock if you have the points)
In the rest of the list I would suggest a minimum sized unit of Kroot (optional) to hold the back objective, protect Pathfinders and push back enemy deployment in night fight, 1 or 2 Pathfinder teams (2 is preferable) and an equal number of Fire Warrior teams. These teams should take the Pathfinders Devilfish and should be 12 strong with an Ui for leadership. The same with the Pathfinders only 8 strong.
Your last Fast Attack slots should have Piranha in them with Fusion Blasters, 1/2 with Disruption Pods, some with Target Locks for split firing (should be common) and if you want , one member with Flachette Dischargers per team, if you do not follow the
INAT FAQ then you might want to use full teams with Flachette Dischargers. This should be your main Anti tank and your source of anti high armour value.
Good luck with the army, a Farsight build is somewhat weaker in my opinion but can be fun to use and offers a different swing on the Tau army.