I made an official post: https://us.battle.net/forums/en/wow/topic/20762176582#1
So the squish appears to have made old world bosses a bit... whats the right word... unsoloable. I believe this happened in a similar way when the zone scaling was applied to the game in 7.3.5. I didn't find an existing thread on this so wanted to get this mentioned. I did a handful of bosses on Alpha and live and compared.
For live, I didn't use my 110 ilvl 943 main for most of these tests, but instead a 101 alt who is ilvl 697. I do reference main a couple of times when I think relevant. On Alpha, I am using my 119 ilvl 259 test character. Both characters are not optimized well and are both BM hunters (since I am familiar with it). I used Ferocity/Tenacity pets.
The tests
Lord Marrowgar, Heroic 25man:
Live: I removed the ICC 30% buff. Boss died in less than 15 seconds. I do increased damage due to the amplified damage from the WoD squish.
Alpha: ICC 30% buff active. No real danger of dying even when standing in fire while bone spiked and Marrowgar Bone Storming. It did take a long time to kill him though, even with the ICC 30% buff active.
Halfus Wyrmbreaker, Heroic 25man:
Live: Got him down no problem, no real danger. Didn't follow mechanics. Approx 90 seconds due to sub-optimal character.
Alpha: Ripped through me and my pet in under 30 seconds, was unable to get him below 90%.
The Stone Guard, Normal 10man:
Live: Killed no problem, approx 1 minute. Ferocity pet never got below 75% hp.
Alpha: Pet was killed in around 15 seconds, shortly followed by my face.
MoP World Bosses (Sha, Galleon, Oon, Nalak):
Live: Challenging to get a true solo test for 101. However my 110 main can kill them fairly quickly, and has done so earlier in Legion (when main had lower ilvl).
Alpha: Barely made a dent in HP before pet and I were killed. Also, Oondasta's beam did over half my HP, and his Roar finished me off a few seconds later. Pet didn't fair much better.
Kargath Bladefist, Normal
Live I knew my 101 couldn't solo this, but my 110 main can do Mythic without problem.
Alpha I couldn't get past the opening trash (Vul'gor) due to flame bolts hitting me for 14.6k when I only have 36.4k hp. I couldn't kill them fast at all.
Note about world mobs from Wotlk/Cata/MoP/WoD
On Alpha, most world mobs from WoD and earlier posed no danger to me or pet since they are grey to me. This includes the elites adult Primal Devilsaurs on Isle of Giants to the elite Blackfang Saberon in Tanaan Jungle (my 101 can kill both with little problem and much faster). On Alpha it did take a while to kill them though, so I decided to do more tests.
ICC 25m Heroic trash with 30% buff still took a while to kill on Alpha, but on live my 101 without buff blasted through trash no problem. I then went to Hyjal, and on live, my 101's single cobrat shot can oneshot Scalding Rock Elemental. On Alpha, my 119 takes a Kill Command and 1-2 Cobra Shot to kill. I think this was the most disconcerting thing of all.
Conclusion
I know the priority for Alpha/Beta is the new content, and rightly so. However since the squish has been implemented, I do hope the old world is reviewed before the testing cycle concludes. I believe 7.3.5 proves old world soloability is very important to many players.