I think something might be wrong with mob spawning..

I'm noticing that hostile mobs are spawning in almost any light level at night and if there isn't a roof over the spawn location. This is really annoying to deal with, because even with lots of torches, they still spawn. Is this a bug or should it be happening?

There's a mod that tells you the current light level.

You could try that on every single block on the spawn radius

There's also a debug menu that does that

This is what I mean..

I still see plenty of places for them to spawn. i find they spawn even in the slightest dark spot.

We just got equinox'd ;P

Is this in EMC or in other servers / SSP too?

I can see spots where the light level is low enough for mobs to spawn in that pic...

You should use monster spawn highlighter, then you will see
http://www.minecraftforum.net/topic/1296949-164-lunatrius-mods/

In addition to what other people have said, I think that by partially lighting up an area you actually make it worse in the areas that aren't lit up sufficiently. The server will keep spawning mobs into the few areas that are left until they are too concentrated to allow more. If you are going to light the area, you have to make sure that every block is covered with light greater than 7 or else you will constantly have unwelcome visitors.

I'm not sure if the light value you see in Debug is the level at your head or your feet. I usually over light areas just in case.

You need torches about every 4 blocks.