The gash is uneven... I cannot picture any way a decently trained Librarian could do it, apart form the warp-stuff, but then - why would there only be one gash instead of multiple chaotic slashes?
Fury of the Ancients... you draw a line between the psyker and the target
The only thing that bothers me are those white knee-caps as they kinda blend in with the cloak and this makes the librarian less pronounced. On one hand - that's your color scheme. On the other, consider that Librarians' suits of armor are supposed to be uni-formally blue and mostly the left shoulder pad denotes chapter allegiance. in that light, you might make the knee-caps blue a well, thus making the Librarian more pronounced.
Great points and I appreciate your input. I decided to invert my color scheme because I didn't want an all blue model. I'm using the same scheme on my Primaris Librarian conversion (gravis captain with a few changes) and I like it on there. I think once highlights are on the knees it might help to make them stand out. I also think your comment about it looking better once all done is spot on. I love this scheme for my main units when it's done, but from start to about 80% I hate it and think it looks terrible.