a good yaoi with good storyline..

guess you should be sure that 'romance' is not a main tag.
otherwise the lovey dovey will be the mainfocus (or something lol) anyway, I recommend
http://www.mangago.me/read-manga/koori_no_mamono_no_monogatari/
http://www.mangago.me/read-manga/adekan/
http://www.mangago.me/read-manga/asterisk/
http://www.mangago.me/read-manga/jinjuu_houretsuden/
http://www.mangago.me/read-manga/awairo_emaki/
here also a bit smut but amazing story (my opinion)
http://www.mangago.me/read-manga/zhen/
this one is also smut and not only this- also bdsm.
but the plot, the characters are amzing.
http://www.mangago.me/read-manga/zankoku_na_kami_ga_shihai_suru/

Maybe consider simply switching to shounen ai?
Mo dao zushi is pretty unique since it's narrated like a novel (I think it's also adapted from a web novel?), so you could also try some fantasy/historic web novels for a similar feel

i came across Back in Time to You recently and its so authentic and a good read I would rec this to anyone

its only like 16? chapters though but completely finished and full colour if you're considering reading bring the tissues!!!

I was like you few days ago specially after reading mdzs I wanted a STORY with some sexy scène but the story is important I just came by this story
YOU HAVE TO TRY IT!!
http://www.mangago.me/read-manga/yuuutsu_na_asa/
Beautiful ART beautiful STORY

Heavy story-focused BL are hard to come by in manga form. Novel has a lot of options though, but even then it's hard to recommend because novel aren't being translated. If you can understand a bit of Japanese, BLCD, are more accessible and good alternative source for BL novel.

I would categorize MDZS, besides the extra chapters, as shonen-ai or shonen/shoujo instead of yaoi to be honest. Even then, MDZS is an exception even among its peers of Chinese BL, imho.

But, for manga, If you haven't read them already, they are good title that focuses on world building, relationships development, and plot imho:

http://www.mangago.me/read-manga/no_6/
http://www.mangago.me/read-manga/banana_fish/
http://www.mangago.me/read-manga/vassalord/
http://www.mangago.me/read-manga/komatta_toki_ni_wa_hoshi_ni_kike/
http://www.mangago.me/read-manga/asterisk/

I'm always telling people to read Saezuru Tori wa Habatakanai, but it's my favorite so.. read it! hahaha. I'll also add some of my favorites. Some are lighter than others, but in my opinion, most of them have killing backstories with happy endings, kind of lol. Hope you find something you enjoy~!
http://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/
http://www.mangago.me/read-manga/koujitsuei_no_tobira/
http://www.mangago.me/read-manga/motomete_yamanai/
http://www.mangago.me/read-manga/mahoroba_days/
http://www.mangago.me/read-manga/koori_no_mamono_no_monogatari/
http://www.mangago.me/read-manga/on_doorstep/
http://www.mangago.me/read-manga/mods/
http://www.mangago.me/read-manga/nights_before_night/
((the last one is a -very good- story of one of the characters in MODS, before and after what happens in that manga))