I've seen mixed reactions to the stat rework and its effect on the gym meta, but I'd like to put down my thoughts and open it up for discussion in this thread. Note that these arguments are being made for someone in a moderately high activity area; different arguments may apply for different levels of activity. tl;dr: I think the nerf is bad for the gym meta.
Gyms are easily the most disappointing and tedious aspect of this game. As I and many others have discussed, much of this is due to overly simplistic and boring battle mechanics - which permeate raids as well - but also because fighting through a max-level Blissey against someone who's actively feeding it Golden Razz is oppressive. As a lone attacker, you would need max-level Machamps and good timing (e.g. no Error 29 lol) in order to berry-cap someone with a Blissey. If multiple accounts are berrying at the same time, it's impossible. For lower-level players, there's no hope even against a single dedicated berry-er, and perhaps not even for defeating the Blissey within the time allowance. I get all of that.
HOWEVER. However, berrying requires you to be watching your account constantly for attacks, for which the in-game notification system is laughably bad. Strong motivation decay means that you have to be mindful of your defenders even if there's no attack going on. Against more than one dedicated attacker, a lone defender has no chance. As this site has pointed out, in practice the best way to collect your coins is to just not get attacked at all (of course, you do have to get attacked at SOME point or you can't collect your coins...why not bring back some way to control they way you can claim coins a la the old system?), so deterring attacks in the first place is really the name of the game. Blissey + GRBs did that decisively against all but the most dedicated of attackers. What I've seen over the past few days is higher gym turnover, which is not a good thing in an area where turnover is already fairly strong. Since single defending accounts are no longer powerful enough to deter a single attacker, multi-accounters are given an even stronger relative advantage than they had previously, which is decisively a bad direction for the game to head in.
Again, all of this is in the context of a gym battling system that is utterly boring and in desperate need of a complete overhaul. One can argue that the Blissey nerf was a step in the right direction in the sense that it should never have been as strong a defender as it was - be that as it may, without compensatory measures, the balance that was previously held (and worked fairly stably in my area) has been shifted for the worse. Whenever PvP gets introduced - indeed, that must be at least part of the reason for the rebalance - if Niantic doesn't also fundamentally change the way battling works, I think this change is ultimately bad and makes obtaining the daily 50 coins even more of a grind than before.