I have 1st step and diving tackle on my oldest DT.
Honestly not sure how much diving tackle helps. It seems to have the most utility if you are missing TFL with diving tackles. You could combine it with Power Tackler and you'll probably get a bit of a buff in your success on TFL. My DT does make quite a few diving tackles, but don't know how much that is having 60+ jumping and how much is diving tackle.