I just finished the last of Kimems armor quest on 4/23/09, so the information is relevant at that time.
You can also buy these plates and patterns needed for the quest from Kulvinia Brightflame and Kanazar. These are both vendors in the caravan located around -150 +650. The plates cost around 3-4 plats. They only carry the items if someone sold to them, so sometimes they have 30-40 plates, other times they have nothing. If you don't want to spend time hunting critters for the plates, just wait, they will get more for sale.
You CAN loot the plates and patterns ahead of time.
The plates drop from all the creatures listed above, but usually the higher-level ones. For instance, if you are attacking the gnolls and run into one with multiple weapons, chances are he will have a plate or pattern.
As for patterns, some creatures always drop a pattern (Cliffstalker). The hardest pattern to get is the leggings (from my experience).
IF you aren't able to just buy your armor quest, I highly recommend stacking these quests at the same time (Or at least finishing the Gnollish Tools quest, those plates can get really heavy).
The best quests to stack in the area are The Golden Pick (at the caravan listed above) and Gnollish Tools (starts in Crescent Reach, gives 10-slot sack with 75% weight reduction).
Hardy Seeds (Crescent Reach) is also a good quest to stack with this if you can't heal yourself.
I put this with the plates because all the other blightfire-infused stuff for Kimem drops more often and is much easier to obtain than the steel plates.