If they still haven't gotten it, then their best isn't good enough.
Kill the bosses with the buff, or kill the bosses without the buff. Only the 10 or 25 raiders who do it will know. No one else will know if you did it with the buff or without, so it doesn't really matter.
Buff or not, those who suck will still suck. At the 35% ICC buff, there were still guilds on my server who couldn't get past Blood wing, let alone down Lich King, hell there are 85's who still can't kill him. lol
Killing bosses without the buff is just self gratification since your ach doesn't change if you use it or not. I dislike the debuff myself, but my raid group is having issues with attendance from IRL emergencies with raid members, I'd rather be able to kill bosses and get heroic gear then being stuck on heroic Morchok for Thrall knows how long until the core members in my group can get back on regularly.
The race to downing DS is over. World first has been taken, continent first as well. All that's left is all the realm firsts which is just people grasping at straws(no my realm first hasn't been taken yet).
I'm a tank for my group. A month from now I'd rather have over 200k hp and heroic gear with the buff then the knowledge im only 2/8 heroic and trying to convince ppl I did it without the buff.