I used to use Draw.io a lot more than I do now, and it is a wonderful tool, the only reason I use it less now is because I've been using:

PlantUML (http://plantuml.com/) with demo at (http://planttext.com). Creating most diagrams through a simple markup language that can be version controlled and rendered on demand has been really nice for me, and sometimes I would spent SO MUCH TIME in draw.io making sure my arrows were even, making the pixels line up, making sure I used the right shape with the right font size, etc, that it was liberating to just succinctly describe my data and have it automatically render.

For more complex diagrams or to plan a diagram, I've also gone back to paper. There really is nothing better than a notebook in front of you and a collection of colored pens and stencils.