What you are saying here is that the Sharks were a fairly good team in terms of turning good-ball in to points. I'd agree with that.
It depends what you consider "attack" to be though I guess. Is dropping the ball 10m out from your own line considered part of your attack? I think it is - but it's not something that a new attacking coach is going to have much influence on.
Is someone trying to truck the ball out from deep in their own end 'attack'? Not really, but the attacking coach and probably head coach would likely have input on how we approach it. Likely some of the more positional coaches too.
None of them are coaching to make dumb errors and mistake though and like you say hard to guarantee a new attack coach could do everything else as well or better and stamp out errors.
As far as games where the Sharks spent a whole bunch of time attacking the other team's line and lost, the Broncos game in Rd14 was the only obvious one. There were other games where they probably had enough good quality possession to win and didn't (Rd 1, 3, 5 and 21) but Nicho missed two of those and in the other two scoring points wasn't an issue (they scored 5 tries in each game). For the most part in the games the Sharks lost 5 the issue was getting the ball to the attacking end rather than lack of execution when they got there. There are definitely some attacking deficiencies which contributed to that (e.g. errors, poor yardage sets, poor end of sets, etc.).
I nearly wrote Broncos game but thought oh Burgo will show me a graph that says I'm wrong haha
I think errors, poor yardage sets, poor end of sets all are far from the sole responsibility of the attack coach. Hannay but also Fitz and Holdsworth would all have a lot of contribution to end of sets I'd think - more or less pending field position.
Similarly yardage sets I envisage are not the main focus of the attack coach although he main be involved in planning them, and watching over practice of them.
Not sure who our 'errors' and 'penalties on tackle 2 when we have them pinned in their end' coaches are but they definitely need to be sacked...
Good field position turns into points fairly well so I think overall Hannay appears to be doing a good job, although I don't know how much responsibility he has in achieving good field position. If that is mostly him then probably needs more focus.
Every team finds everything harder against the good teams than the weak teams.