jodyjohnson
Adventurer
I think that's the way to approach "encounter building". It takes relatively little effort from the DM and can create some super interesting situations as the PC's come up with absurd plans and the DM-kobolds react. It creates a totally different dynamic than the set-piece 4e encounters found in just about all the premade adventures.
I'd aim for individual moderate encounters and if they pull the area, hard combined.
Two hards without a short rest between seems like a campaign ender.
But if after play and char op it might be needed for a truly hard challenge.