You can cover every position from the bench actually very easily. A bench of Laidlaw, Tuilagi and Hogg covers every position. So would Care, Farrell and Kearney or Phillips, Farrell and Roberts even. Then add to the fact that you would expect at least one or two of the starting backline could change position if needed and it isn't that much of an issue. Having said that though, I would have much rather Hook had been on the bench in hindsight than ROG in 2009!
You're overrating the use of utility. And also the effectiveness of Hook's utility. His utility didn't exactly come to much use at all in the 6 Nations or the Autumn Internationals did it? Players need to be able to be good enough in their position outright in my opinion, and it is hard to argue that Hook who can't keep Biggar out of the side is one of the top 3 fly halves in the British Isles. Also I dispute the "do the job if required" bit as well, Hook is a reknowned choker and didn't exactly do a job required against France in 2011 under pressure.
Behind Sexton, the quality at 10 isn't great. Biggar I think is underrated, but has only recently transferred his regional form into international form. Farrell is overrated and is imo a limited player bigged up by Guscott as the 'ice man' despite crumbling under pressure on a few occasions. Behind them there's Laidlaw who I question his quality at 10 (he's a better 9 imo), and rookies like Madigan. Hook isn't far behind some of these players, and is probably a little unlucky not to have played more for Wales over the past couple of seasons. I'm not in the camp that Hook is the rightful Welsh 10 and Gatland and Howley have been idiots for not picking him, but I'm also not in the Hook = rubbish camp. I think he's still a very good player who's fallen a little out of favour. He's not a past-it player like ROG.
If Biggar weren't the starting 10, maybe if an on-form Priestland was starting, then I'd still have Hook on the bench over Biggar.
And I still think his versatility can come in useful. We didn't lose many players to injury during the 6 nations, in fact we were able to put out the same backline for every game. Doesn't mean Hook's versatility can't come in useful. Look at the last Lions tour, at one stage Phillips had to fill in at centre, unlikely scenario's, but they do happen, and are more likely during intense, all on the line tests such as a Lions tour which only comes around once every 12 years for the Aussies.
Rubbish. No way would the Ospreys "be obliterated" by Wales. The Ospreys have an equal front five so the pack which Wales has used to win their most games would be cancelled out. Also the Ospreys have a better scrum half, and Wales' backs are overrated. Beck and Bishop could defend and negate Davies and Roberts, and in fact the much hyped Scarlets backline barely scored a try against them this season. So there is no way that they would be obliterated. I don't see how Wales could "obliterate" the Ospreys or where they would get any substantial advantage, in fact when was the last time Wales "obliterated" anybody to be honest. Their backline is blunt (see November 2012), and is just riding off the coat tails of the immense pack which the Ospreys have most of anyway.
I may have over-exaggerated this. However I still think that Wales get a lot more out of the Ospreys players than the Ospreys manage. In your opinion there's not much between the Ospreys team and the Welsh team, but that should mean that the O's should have lifted a HC by now because the Welsh team have proven their credentials by securing Grand-Slams and reaching World Cup Semi Finals.
For every Sexton there is a George North, just a couple months RaboPro12 action and then scored 2 tries on debut and was doing really well. There are numerous other cases of players taking to international rugby really well, Fofana is another example. So just saying Sexton (who actually I think I remember playing really well on one of his first caps vs South Africa) doesn't suggest a pattern. The fact Sexton hasn't always matched his Leinster form says more about the coaching methods of Declan Kidney than it does about international rugby tbh.
I take that as some players are naturally able to handle international rugby. Some can shine at domestic level, even at HC level but struggle at international. This to me shows that there is a step-up in intensity.
Anyway, we're probably quite far off topic now. I admit that this is just my opinion, and it may well be wrong.