A few things you said don't seem to have been clearly addressed -
1) YES you can try some other clearomizers if you have EGO batteries. A LOT of people like the EVOD. A lot of people like the ProTank or ProTank Mini (the mini is Ego-sized, the big one is...bigger - it comes with a collar that flares out to it's diameter). That's the good thing about an Ego - you can use almost anything you like to feed the juice.
2) Glass isn't needed for "gunky" or dark juices - glass IS needed for certain juices that can corrode plastic. Do a search for "corrosive juice" to find a list. Things like cinnamon, or acidic flavors (lemon?) tend to require glass.
3) What gets gunked is the COIL - on many clearomizers, that's easily replaced for like $1, and you wear them out - but you CAN and SHOULD clean them to keep them going before that. Hot water rinse does it for me with my light juices. If you are vaping chocolate or coffee, you may want to learn more about cleaning gunk off a coil with a "dry burn" and maybe a vodka soak...
4) What probably caused your burnt taste with a new clearomizer was not getting enough juice to the coil before you started vaping. How to do that, and how hard or easy it is depends on your model - which I don't know. Some models (like the EVOD I suggested above) all it takes is a couple puffs without pushing the button, and you're usually all set. Once your coil has a burnt flavor, it may not go away - depends how bad it is...