Agree on both counts @moonchild and @SuibianX - The sisters were given more presence (okay, that's not the right word.. emphasis?) in the drama than novel mainly thanks to WWX and of course the actresses themselves.
Yes, Jiang Yanli didn't have much impact on me either. I don't know how they intended in the novel or if that's how the drama wanted to portray them. Most of their (Yanli and Wen Qing) scenes were described as having happened in the novel instead of narrating the scenes as they happened (I don't know if I am phrasing this right). I am not sure but maybe that's why they weren't a big deal there, while in the drama they actually played those scenes.
In any case, even though I wasn't taken with Yanli at all at first, her existence was truly a gamechanger at every occasion. She and WWX interfered on each other's behalf and both of them suffered for it.
WWX at the victory feast of Sunshot campaign
Yanli at the hunt organised by the Jin clan
Jin bro in law inviting WWX for Jin Ling's birthday for her sake
Yanli chasing after WWX at Nightless City
Given all this and the importance of her relationship to WWX, it became hard to ignore her (Yes, I am guilty of having tried to do that at some point precisely because I didn't think much of her) - Also, she was in so many of the endless memories of JC and WWX. This also might be why her absence (and the cause for it even partially being WWX) affected JC and WWX's relationship so much.
But all the discussions we've had in the forum about scenes with Yanli and her OST which I heard only a few days back, are making me rethink stuff