I'm not against the FoS achieve thing. I think it's a step in the right direction, in a way. The problem I see with it will be this:
1) Guild runs normal. Gets gear.
2) Guild runs heroic with debuff/buff/nerf/whatever..... gets gear
3) Guild run heroic without buff while in full set of BiS..... claims awesomeness.
It'll be apparent to those who raid, just from the date of raid completion, etc, what the real story is, but there will be people who will "game" it.
But again, that's why I advocate very strongly the unforgiving heroic mode. No raidwide nerfs. Only boss specific nerfs/fixes to correct mechanics that are not working right. Leave it intact as the competitive mode raiding.
No one tanks in a void.........