I think the math you quote is close, but not quite right. There are 12 "safe" Dem districts where there are indeed 2 Dem candidates per House slot; that's a potential of 24. Four "single shot" competitive districts brings the potential up to 28, and LD13, where Dems are running 2 candidates, yields a potential of 30. From that point you can theorize about long shots - one of those theoretically "competitive" districts is LD16, which will be hard for Dems to win, though possible, so the pessimist will say 29 possible, as you did; and LD17, while not usually called competitive (using the AIRC's metric, for instance) is not much more Republican-leaning than LD16, so the optimist will say 31. And the Democrats are expecting the single shot approach to yield higher likelihood of wins in the districts where it is used.
So the bottom line would be that the redistricting ended up with enough of a shift to the right that it will be difficult to gain the AZ House, but not impossible, and certainly not impossible to tie (which would also have a big effect on legislation next year). The AZ Senate math looks better for Democrats because there is a candidate for every slot.
I think the math you quote is close, but not quite right. There are 12 "safe" Dem districts where there are indeed 2 Dem candidates per House slot; that's a potential of 24. Four "single shot" competitive districts brings the potential up to 28, and LD13, where Dems are running 2 candidates, yields a potential of 30. From that point you can theorize about long shots - one of those theoretically "competitive" districts is LD16, which will be hard for Dems to win, though possible, so the pessimist will say 29 possible, as you did; and LD17, while not usually called competitive (using the AIRC's metric, for instance) is not much more Republican-leaning than LD16, so the optimist will say 31. And the Democrats are expecting the single shot approach to yield higher likelihood of wins in the districts where it is used.
So the bottom line would be that the redistricting ended up with enough of a shift to the right that it will be difficult to gain the AZ House, but not impossible, and certainly not impossible to tie (which would also have a big effect on legislation next year). The AZ Senate math looks better for Democrats because there is a candidate for every slot.