I'm not sure it does simply come back to Rooney. We had games where we never picked up the tempo/intensity last season even when Schumacher was in charge. It was only when we clicked up a gear that things came together - I'm recalling the home games against Blackburn and Norwich that we ended up winning easily but really should have been dead and buried in before we took control. Also, going back two years we quite often ground away in the earlier parts of games and then only in the last 20-30 minutes, usually playing towards the Devonport End, did we take control of games and blow teams away - the Ipswich and Sheffield Wednesday games come to mind.
There's no doubting that we're not playing very well at the moment and obviously Rooney is the man at the helm so he undoubtedly has some responsibility but I think we all have a tendency to remember the positive parts of the last couple of seasons much more than the negatives. It was around this time two years ago (perhaps a little earlier in the season?) that we lost at home to Swansea and Millwall in the space of a few days and my recollection is that in those games we played pretty tepid, ineffectual football. Also, haven't there been stats that show that even in our 100 point League 1 title-winning season we hardly won away from home (perhaps I am misremembering). So I am not entirely convinced that things are that much worse than there were this time last season (although I do think that the current stats for possession and touches in the opposition box etc do paint a pretty depressing picture).
It was interesting to me that even last night, in between noting how poor some of Argyle's play was, the Sky commentary team (especially the co-commentator - I don't know who that was) were also saying quite a lot of positive things about some of attacking play and noting that we were posing a threat to the Norwich defence. I missed the start of the second half but got back to the game just before Norwich scored and at that point the commentators were saying how well we had started the half and how unfortunate it was that we had then conceded despite that good start. So, I think the lines are finer than many make them out to be - I mean, they are obviously not 3H pencil fine but perhaps they are more 2B than 4B or 5B...!
When people were venting at Foster last season, I repeatedly said that they were misremembering how frequently we rode our luck under Schumacher. I still feel the fact we had harder games in the second half of last season and the loss of key players in January were more important to our downturn in form than the change of manager.
So I would like to think I am pretty objective about this, and I would say that the games you cite from the Schumacher era were nowhere near as bad as we have been this season. As I recall it, Argyle pretty much took Norwich apart at Home Park and never looked in trouble. In the games v Blackburn and Swansea (you could also add Huddersfield, Sheffield Wednesday, Stoke and Rotherham) we were on the backfoot at times and to have won five and lost only one of those six undoubtedly flattered us. But they were all entertaining games where we produced spells of good football.
Since the second international break that really hasn't been the case. To have taken four points from the Portsmouth and Watford games wasn't fine margins or breaks going our way, it was utterly freakish. We created virtually nothing across the two games and yet scored three goals - Gray conjured up two from nowhere and Obafemi scored v Portsmouth by chasing down slapstick defending. When a long punt from the keeper provides an assist for a goal in pub football, everyone laughs so to be gifted a goal that way in the Championship is unbelievably lucky. Things like that won't keep happening and we will start losing every week without a massive improvement.
Obviously the away performances have been even worse. We had one four goal defeat last season to the league champions, after a putting in a decent first half performance. We've had three already this year, to three teams in midtable or worse.
I don't think this is simply down to Rooney. But as I said in the original post, the lack of intensity seems to come from a combination of a lack of quality, confidence and preparation. The latter two are things that the coaching team should be able to affect.