A lot of Kalafina songs depart heavily from what Kajiura is famously known for. You can tell it's a Kajiura song if you were a pre-existing Kajiura fan, but a song like Hikari no Senritsu is completely unlike anything she made for FJ Yuuka or Seesaw before. Plus Kalafina dipped into so many different genres that all that music being composed by a single person is nothing short of amazing. Imagine a composer who's primarily known for classical choral gospel-inspired soundtracks being able to write not just good, but amazing rock, symphonic rock, heavy metal, enka (ish, Sandpiper is very enka coded), folk, waltz, electronic, jpop, chamber pop, synth, progressive rock, new age, with traditional Japanese and Arabic/Egyptian influences mixed in. And with harmonies and intricate vocal arrangement and layering in almost every song.
When I describe Kalafina to my friends, the closest I can think of is Evanescence, and even that is not close enough to describe Kajiura's work when she was in Kalafina. The diversity is shocking when you think about it, and I don't think many people on this planet can do as many genres as Kajiura had with Kalafina.
Now I really wish she used what she leaned in Kalafina and add it to her OSTs. Kalafina's rock songs are the best, bar none. Imagine an electric guitar focused OST rather than a violins and strings for once.