IMO, more than anything, they need 5 guys on the OL who can flat out hold their blocks against four and five man fronts. The Ravens earlier in the season relied on extra blockers with Ricard and a TE to block the blitz, it worked against Denver who blitzed us at a rate of 56% but Cincinnati was the first team to adjust to this and had 6 DBs back and pretty much bet on them covering longer then we could find a guy open. They came in with a variety of looks and once Mekari went down the OL seemed to follow suit. If they can have 5 guys who can block without the need of having too many extra blockers it will make a world of a difference.
As far as Cover 0 goes, that Dolphins game Miami decided to play the sticks and make it hard for us to throw short crossing patterns with a LB and CB crashing down on those slant routes. Watkins decided to have a nightmare game by pulling up on a TD pass against the blitz(Good throw given the pressure) and then fumbling on a slant that was returned for a TD. I liked some of the screens we saw given how hard Miami was playing against the sticks, some of it worked and better blocking on one play and better vision by Duvernay and he could've had a huge play. Against Pittsburgh, I thought we had some success against the cover 0 looks we saw. Pittsburgh threw a bunch of delayed blitzes that we had trouble with and I think on some other plays the OL didn't do a good job with zone blitz packages we saw. Outside of the Miami game, I don't think the cover 0 looks were that big of a problem.
I agree that Roman needs to be more creative, that's #2 on the list IMO but they brought in a passing game coordinator this season, I wonder how much of the onus for the passing game falls on him compared to Roman. Roman calls the plays but it's not only him we have to single out here. I think for as long as we've all been watching the team it's just lacked creativity in the passing game, you made a good point about Harbaugh needing to do self-reflection, I couldn't agree more.