I agree with you. I had killed hundred of Lizzogoth and heretofore. Unfortunately, I had never a chance to got to level 4 maps.
To be candid, I think that it is too hard to go to the level 4. I will suggest to use accumulated system to go to next level. (I think someone had suggested but I forgot ...) Let's say 10 maps (no matter 1, 2, 3 or 4) can be combined.
I will suggest there is a tool which can be purchased from Shop to upgrade the gem.
-The tool can be used for 100 times
-It can combine lower grade gems to a higher grade. e.g. 3 to 1
-Meanwhile, we can financially support the server.