5% a couple of times on a raid that was plagued by early mistakes was a very good result.
So an extra 1% from each dps + a little more from the tanks and he'll be down.
A few things you can do for Monday:
Check enchants, we've got some team mats so get whichever are best for your class even if your item isn't the best and you'll be upgrading as we need the DPS now.
Flasks - if tanks weren't using dps flasks then use those next time (I'm assuming different flasks are still used for tanking v dps)
Food - get 300 stat food instead of 250/275 feasts.
Potions - get 40 ready for 20 pulls, pre-pot and remember to use them again with your cool downs.
Talents - double check that you have the best talents for this fight, we only need a small increase so a talent choice might just make all the difference.
I'll try and stock up on potions and food but if you can at least get the mats we have plenty of high level cooks, alchemists, enchanters, scribes and tailors.
See you all Monday for the kill
EDIT: As Akee mentioned check your reforges! and if you got plenty of VP think about upgrading a piece or 2 of gear (weapons and trinkets usually are your best choice) if there isn't anything left for you to buy.