I think the tuning is fine. It is not pug-friendly, but that's not really the audience, and in any case I think pug success rates will improve in the coming weeks.
Some people of course got lucky and had 5 wipes give or take to finish. I'm sure many of those groups happened to be composed mostly of people on their mains who had done the fights in normal. A pug with a less distinguished pedigree is going to need lots of explanations, it's going to wipe a lot, and it may not even get anywhere.
I went through three different pug groups to get down Blackfuse; the first two fell apart without a kill. Paragons down in about 5 wipes. Garrosh: 16 wipes, 2 pug groups, still no kill. In every case the groups I was in were totally new to the fights, save 1 or 2 people on alts who had done them on their mains.
The hardest part,or most time-consuming at least, is the "unstickiness" of pugs. Invariably, someone ditches after a couple or three wipes, a replacement must be brought in, the fight must be explained all over again, etc. Worse for healers and it's usually a crippling blow if a tank quits. But that's the life of pugs I guess. (Dear Blizzard: fix the tanking situation in this game, idc how you do it, but it is so tiring to wait half an hour or more to find that second tank no matter what you're doing in the game, as the list of DPS waiting to get in keeps piling up...)
EDIT: I guess I should point out I'm less enthusiastic about W4 than the other three. Each time after completing wings 1-3 for the first time, I was stunned by how perfectly tuned they were. As for W4, I can only somewhat grudgingly accept that the tuning is "fine" for the position it occupies in MOP raids. Bottom line is, some players/guilds/groups are going to be excluded out of this wing for the first weeks at least... Which I guess delivers on the goal of seeing a new boss per week.