The 15'' has a 76WH battery. Maximum allowed by the FAA is 100WH. I doubt the 33% increase in capacity would help as drastically as you imply.
Well, seeing as there are actual reviews of the Razer Blade why don't we look at it?
http://www.ultrabookreview.com/10704-razer-blade-14-2016-review/
Lets look at the battery life, it gets 6 hours watching Youtube at 1440p. It also uses a 70WH battery.
If Apple, kept the 99.5WH battery from last year, we'd be looking at 8.5 Hours of 1440p youtube viewing.
As for heat, the only time it really starts to heat up is when it's gaming and under full load, but being realistic, you're not going to be gaming on your lap. You are also assuming that Apple can't do better as far as cooling compared to Razer. Oh, and do you really think the Radeon 460 won't heat up quite a bit while under full load? That's funny.
As far as throttling, the Razer was throttled slightly after a while of gaming, however they said the throttling had a very small impact on performance. With that being said, that slightly throttled 1060 will still blow the Radeon 460 out of the water performance wise. For all we know, apple might also throttle the 460 under extreme load.
At the end of the day, from actual reviews of the Razer, and then keeping in mind that it has a much smaller battery compared to the previous MBP, it is not nearly as impossible as some of you like to think it is to stick it in the previous MBP enclosure and get still great battery life while significantly upgrading the performance.
I guess that shaving that tenth of an inch off was worth giving up that performance in Apple's eyes.