Using Farsight as a speedbump is an interesting idea, but I'm not too keen on it. It depends what is incoming, I guess.
In the three games I played with him on Saturday (W/D/L) I faced Blood Angels (a tri-raider list and a Mephiston/ Sanginor jump pack list) and Deathwing. Speedbumping with Farsight against Land Raiders would not have worked. I could have Death or Gloried with my lone Fusion Blaster suit or with Farsight, but against AV14 that's a tough nut to crack. More likely they would have tank shocked me into a tight formation and Flamestorm cannoned the squad into little pieces. The TH/SS termies wouldn't even have needed to get out. Speedbumping against Meph/ Sanguinor results in two of the best close combat models in the game hitting you on Turn 1 or 2. Hmm.
Against Deathwing, while I didn't speedbump with Farsight, I was much more aggressive with him, and basically used him to threaten the enemy objective, and he wound up taking on half the enemy army by himself, but he did so by keeping his distance, and moving around. He pulled several units towards him, away from my core, but he did not assault and kept shooting until the last moment. Even when he was charged, he was in cover and held for several rounds of fighting.
A Farsight unit is approx 700pts of superb shooting, and letting the enemy tie that unit up in close combat with anything that is half-decent is handing the game over. Unless you have spent several Turns whittling incoming close combat threats down to manageable levels with shooting, they are going to shred your 700pts and then the rest of your army can be picked apart at leisure, given the gulf in points remaining on the table. Farsight can (and did in my games) hold his own in combat and even win, but I am spending those points for shooting ability, not melee. With Farsight my speedbumps are my Pathfinders and my other crisis suits and, in KP games, my Fire Warriors.
Farsight could be tooled up for speedbumping, I guess, with lots of shield drones and shield generators, Iridium Armour and Stimm Injectors, but it's still a lot of points for a tarpit. Say 581pts for Farsight and 3 Helios Retinue all with shield drones. Gimmicky perhaps, and I might try it to see how it works, but that is one expensive tarpit.