I guess I should write what I think we should do.
My position is that I'm certainly willing to trade Hanley or Panda for 70 cents on the dollar, but not 10. I'm not sure what the trade market looks like for them, but I'm guessing it's closer to 10. The following reasoning is based on that assumption. (Then again, one never knows: knock on wood and send a prayer to Vernon Wells, patron saint of lost causes....)
Let's say you keep Pablo (or Hanley — the same ideas apply). A year down the road one of three things has happened:
A) Pablo has a great season, the kind of season that would have justified the FA investment. In this case, you win! The player's value, both to the Red Sox and potential trade partners is pretty much restored; also, our 2016 team is probably really good.
B) Pablo is merely okay, say 1 WAR. In this case, you've not gotten much value out of the roster spot and payroll allocation, but you should be able to live with it until you have a better option at the position. Maybe this is Shaw extending his big league track record and earning more playing time; maybe it's Moncada taking the Mookie Betts approach to the high minors. We have a lot of interesting infield prospects. But in the meantime, a Panda who's at least posting positive WAR should be tradeable on more attractive terms than a Panda who's deep in the red. Someone with a need might be willing to pick up a meaningful portion of the deal.
C) Pablo is 2015-level bad, again in 2016. Unplayably, -2 WAR bad. In this case, you have to release him, even if you're just replacing him with Deven Marrero or Marco Hernandez.
But what have you lost? His present trade value is near-zero or maybe negative, so you've lost the difference between that trade value and the value of the outcome of the DFA. You've also been hurt by the poor play in 2016, and the opportunity cost of the roster spot, but you need to weigh that against the possibility that a player with his track record will return to form or something like it.
How long you should be willing to continue the experiment depends on how good the rest of the team turns out to be. If we shape up as a 70-something win roster again, it should be all year. But if the rest of the roster looks like a potential contender, we should give him through May — say 250 PA — to show signs of life.