Skyreach run is easy, you can even run it with /follow no need to broadcast it. i think you just gave up too easily.

and for dungeons 2 heals + 3 hunters is ideal, pets can manage almost anything and if they can't you cant just cycle rez them, and 2 atonement priests, or Druids can auto heal 90% place and power heal though any boss mechanic. once you make it past the 680 ilvl 5x hunters are just plain silly, BM pets will solo everything, all you need to do is run around. (but remember to tag!)

plus, if you have druid heals, the same team that does current dungeons with ease will also run old dungeons on timewalking weekend. specially if you run 3 hunters + 2 druids, since you can que all hunts as dps and one druid as heal and another as tank, and keep 2 heals inside the instance.

pala heals can do the same, but you don't have an atonement effect so it can get busy. (tho 5x pala tanks rotating agro work, as usual.)

also tank + 4 atonement healers can farm trash on current raids. and for old raids 5 manning it is 99% of the time overkill. wish blizz added some difficulty to the old raids. BUT if you want rare stuff you can clear the way to a boss, then kill it with every alt (sharing lockouts). you can get as many as 50 rolls a week at rare mounts. once have all the rare drops its a bore... but its addictive as you make your way to them.

anyway as for the OPs questions:

1) yeah, dungeons are getting dumb with all the fires and jumping and moving... its not wow anymore. and legion is even worse. but for WoD most requirements can ever be solved abusing CDs or abusing the power of coordinated burst DPS.

some bosses i found to be only doable planning on sacrificing alts. think Garrosh in the pandaria raid. its really hard to complete that fight unless you sacrifice some alts. (he does some one hit kill attacks)

2) they change the way the game works, the last change which pissed me off to no end is the removal of guild item control from Addons. previously you could have an addon move items around in the gbank... now they are locked.

3) not as fun as it used to be, but other MMOs are still trash compared to wow. and ive tried them. (not just talking about boxing here, im talking gaming in general)

4) ofc you can, old raids have been retuned to be soloable for the most part. kill abilities are still there, so you still have to avoid garrosh slams, yoggsaron's insanity, etc, etc.

current raids can be done by groups of boxers, on MOP did a few (flex) and they were really fun, the problem is that coordinating with 2 other people seems to be harder than coordinating with other 9 or 19... weird.