From low spenders/F2P:
C0 without homa and Zhongli,She's a decent dps,T1 level,if you lack good a pyro dps,she's a good addtition to your team,but if you have other competent pyro dps like Diluc and Klee,you can safely skip her.
From dophins and smaller whales(that is if you get lucky with homa):
C1 with R1 Homa and Zhongli:T0,a powerhouse,beats diluc with WGS completely, her power level is only after Ganyu.
Frome mega whales:
C6 with R5 homa:The best dps in the game so far,if you are into stuffs like 6-10 sec abyss speedruns,she's your choice.
Recommend comp:Hutao+Xingqiu+Zhongli+a fourth slot
An entertainment showcase from mega whale(all C6 with R5 BIS weapons):C6 diluc vs c6 klee vs C6 Hutao dummy test
The general agreement is Diluc's very versatile and easy to use,the best dps from early to middle gaem,but if you want to do big numbers and speedruns,he's not the best choice.Maybe a claymore with CD can change that?
Edit:Information is gathered from bilibili and NGA