Just want to post my opinion, so anyone behind me can get one more view on things. After dinging 45 in Dulak I returned to PoK for some gear upgrades and such, and spent a while trying different areas.
I returned to Dulak, killed some uglies. Tried Oggok, killed some even ugliers. Thought, what the heck, lets make the run to CoM and give it a whirl.
WOW
To be fair, I have my friends 65 Druid following me around, so I can't reccomend CoM at 45 to soloers, because almost every pull I've had was at least two, and sometimes three. There was also the occaisional yellow wandered add that might spell disaster for a soloer. I'm sure some areas can be singled, but with druid buffs and DS, getting two everytime was no big deal to me.
I would pull with slow, kill the slowed one (in most cases in under 45 seconds), then kill the add that I didn't slow. The mobs there deffinately hit harder than in Oggok/Dulak, but they also seem to have 1/3rd the HP. There is also a MASSIVE difference in difficulty of the various DBs. Some of them I can kill in under 30 seconds with losing 5% of my health, others take several minutes and require a fair amount of druid healing.
So, if you are two-boxing or have a friend to tag along, IMHO you will be hard pressed to find better exp for your time and effort than in CoM. I went from 1 yellow into 45 to dinging 46 in roughly 90 minutes. And that was with a no-res death in the middle due to a massive train from somewhere deep that wasn't announced.
CoM might be hard solo at 45, but it is a two-box haven.
-Dontae