I thought I would just be insta killing everything with her. I actually kill shyt faster with Ayaka and Yanfei.
Using her normal attacks in conjunction with her E skill, just thought shyt would die faster basically.
Every now and again though I'll just instantly wipeout an entire mob with her, not even sure how lol
Best way to use her is:
Pair with electro for Superconduct. (-40% physical resistance for enemies)
Pair with Zhongli. (his shield gives -20% physical resistance for enemies)
Attack normally, press E. You get a stack of Grimheart. Once you have two stacks, hold E and that will give enemies -16-25% physical resistance, depending on your skill level.
Also holding E will do 245%-442% physical damage, depending on your skill level. This is most likely how you're randomly killing an enemy.
Best rotation for your burst is E, burst. The burst itself gives one stack of Grimheart so you'll have two then. Normal attack 4-5x, hold E, then normal attack until your burst ends.
Also what artifacts/stats do you have?
Fred.