I'm not sure where you got those numbers because what I see on BasketballReference is different for all of them but not by more than 2-5 per player so I'm not going to waste my time trying to correct them. We're losing shotblockers, there is no way around that and they will take a dip in that in the rankings but since the Suns were 15th last year, I'm not sure if it matters that much if they get worse in that category because it didn't help them being middle of the pack last year.
Baynes will alter shots, like he did in Boston, and his block numbers aren't that important IMO. I think part of how Holmes was able to get so many is he was a question mark on a lot of scouting reports. Other teams didn't know what to expect from him at first and it took some time for them to learn he is a threat to block shots. He still did ok throughout the season for a backup but they both allowed virtually the same exact shooting percentage within 6 feet, Baynes was 55.1% & Holmes was 55%, with a .1% difference, I don't think we'll see much of a change in overall defense from the backup spot except Baynes provides more leadership than Holmes for the 2nd unit.
With the others, replacing Jackson, Melton, and Warren with Cam, Dario, and Rubio, I think we'll have better overall defense even though there will be less measurable stats like blocks in order to show that. You'll need to look at advanced stats to the see the difference there.
Based on the number of blocks by teams though I'm not seeing any real correlation between winning and blocks so if they fall from the middle of the pack, so be it, so long as they can play better defense overall.