By range, Azra can cast for hundreds of meters, possibly kilometers.
By amount, in-battle Azra has a certain amount of PSI that she only gets back by killing enemies, which she expends to cast spells. We don't get a good lore indicator of her limits on number of spells cast.
On my nearly-finished-NG+ file, she has 3225 PSI, with spells costing from 10-75 PSI each.
As somene who's actually read Worm, I believe Grue takes quite handily, especially considering the fact his darkness manipulation's feats seem to be above the baseline Azra has dealt with, especially since it can actually steal powers.
For information's sake, certain revenant cloud themselves with magical darkness to make them harder to hit. Azra with the book can dispel this across the range of the entire screen (usually around hundreds of meters) for a few seconds. But there's nothing indicating a super above-baseline level of darkness that can't be dispelled by light.
Grue's clouds negate all sorts of waves. Can't really hear in them either, and they made certain powers not work even before his second trigger due to this. Light's still a wave, I don't think he'd be nearly as effective if strong lights could override his effects given how many tinkers the heroes have at their disposal.
Being second trigger means the darkness comes out a little slower but has straight up power theft and blocking now. Obscuring both his location and the powers themselves would make it hard to hit him with spells, and against an unknown enemy he's probably gonna flood with darkness right off the bat for safety.
Dragon Fire causes fire to rain over the entire hundreds of meters radius, so the location being obscured shouldn't be a huge issue. She can also still hit enemies surrounded by darkness with her Lightning while normal attacks would miss, but this could be game mechanics or due to them moving slowly.
She also has Push Back to telekinetically knock everyone in a radius away from her.
Telekinesis to deal with his shadow seems like her best option honestly. The main thing though is that she has no clue what the actual deal with the shadow is, as the moment she's inside even a bit, her troubles increase exponentially.