Ok,i will open few secrets here
If you get your pages delisted from google serps,you must be didn't make elementary niche analyze,what is approximately keyword density for your niche (for your keyword) but used dpgp with default settings,this can be a reason,google find your doorways overoptimized and delist it...
If you dont wanna spend your time analyzing all these nuances and tweak your pages detailed,make thin settings etc,you better use another technique- "fire and forget",make thousands pages daily(using large lowcompetition keyword list one time),submitt it,get decent traffic and forget about these pages!
I know many guys using our stuff get up to 200.000 uniques a day making doorways at freehosts such as 100mb etc.It's most easiest and fast technique,this way you dont need spend a lot of time learning
SEO tricks etc