Does anybody else use definition practice for tone practice like I do? I try to say the character or phrase correctly and know the meaning before I mark myself correct.

The reason I do this is because:
a) it reinforces tones, which I suck at
b) sometimes I think about tones too much in regular tone practice and get it right without really memorizing it
c) it can help with tone changes and pronunciation (when I listen and compare with the audio)
d) quasi-speaking practice (I'm trying generally now to say Skritted words aloud to practice my vocalizations).

I do, but I don't grade myself on the tones, because I also use Anki for reading practice.

I try to think of the reading to help me with the definition, but I don't score based on it because I know that active pinyin practice is coming soon! (I've actually written the skeleton for it; I just need to working on the typing logic until it's really good.)

Saying the words aloud as you practice them is good. Perhaps making short example sentences using them is even better, if you can spare that much concentration.

Yes, I do use definition for tone and pronunciation practice, too. Only drawback is I do grade on getting both pronunciation and definition (less strict on tone), and that has brought my retention scores down. Probably a more accurate retention figure, however.

I have started to separate the practice: work on writing (my favorite), then tones, then definitions. I wonder if others do this, too, and find it helpful. Or is it a better challenge to have them all mixed together?

I also grade myself on pronunciation and definition. If I get the tone wrong, I mark it incorrect. This might be a bit inefficient since I'm also studying tones individually, but I figure there's no harm in reinforcing them.

I was using Anki previously for reading practice, but I've stopped now since I can do it in Skritter. Still using it for sentences though.

I do find it if I study writing and meaning mixed together sometimes I "know" something because I just reviewed it so @arp, your method does make good sense.