I watched a lot of CDrama but most of them are not deep in fact mostly cheesy xD if you want a real "deep" drama my suggestions:
1. Nirvana on Fire (historical and the best so far, if you like it try Advisor Alliance)
2. Battle of Changsa (Japanese Era)
3. Legend of Concubine Zhen Huan (another historical drama with harem)
4. Love Me if You Dare (modern adapted from novel, if you like it perhaps you're gonna like the other dramas from the same author ie When a Snail Falls in Love, Memory Lost..all about crimes but among all Love Me if You Dare is the best).
5. The Surgeons (worth to watch if you curious about doctors' life in Beijing).