I'm using CE4's & a few CE5's right now (the CE5 is just a rebuildable CE4 I think). Out of 8 so far, I've had 1 bad 1. The coil didn't heat up properly so it barely hit. I drained it out and it worked fine in another 1. I dunno if it was just coincidence, but it was the thickest juice I've had, which is known to not be so great in this type of wick clearo. Other than that, I have no real complaints w/ these. I have 5 in rotations right now w/ different flavors, and I'm still using the 1st 1 out of the bunch, which hits/tastes fine.
Not everyone is gonna get this type of performance w/ cheap gear tho. I prefer vaping thin juice which is better suited for these, and not too much more than 1 mL a day total. My typical button push is only for 2-3 seconds, and if someone was taking bigger puffs I'm sure there'd be burnt hits. I have a nice nicotine strength, so I have no use or desire to try and make big clouds. At any rate, I think you probably have a bad clearo, cuz even my thick dark juice still worked in another clearo.