Bugger,
The only problems I've seen with Sierras have been when they were driven too fast and then used at short range.
Most cup-and-cores or any type work best when driven no faster than about 2800 fps at the muzzle, and 2700 with a heavier bullet is usually better, because the bullet will retain more velocity at longer ranges so still expand, yet not have as much tendency to come apart up close. Have shot many animals with the 160 Sierra GameKing from the 7x57 at around 2650-2700 and never had a problem from 100 yards to almost 400.
Have seen the 130 Sierra .270 GameKing come apart a few times when driven at 3000 fps or more on closer game, though it usually works fine from 200 yards out. In general, if I want 3000 fps out of a cup-and-core and might shoot something under 150-200 yards, the Hornady Interlock is the choice.
When I used the 105 Speer Hot-Cor in the .243 the muzzle velocity was around 2800 fps, and only one bullet came apart--but the core still penetrated and killed the deer. When I used the 140 Speer Hot-Cor in the .264 Winchester the muzzle velocity was around 3200, but I only used it for deer in open country, minimum range about 200 yards, and the result was always a wound channel and exit of about 1".
Have only seen one softpoint cup-and-core not expand (or at least not expand much), a 120-grain Nosler Solid Base from a .257 Roberts at about 2850 fps. Shot a big mule deer buck in the lungs broadside, just behind the shoulder, and he went 200 yards before falling. The hole through the lungs was very small, as was the exit. In fact only found one tiny drop of blood, right where he was shot.
But anything is possible, and you never know when some bullet company tweaks the design, or somebody on the assembly uses the wrong lead alloy for the cores, or does something else to screw up some bullets. But those are the exceptions and not the rule.
I shot a doe in the shoulder with 165 grain Sierra Game King out of a 06. The bullet didn't enter the chest cavity. The doe tried to run off on three legs. And I had to shoot her again.
My brother-in-law shot a Bull Elk with 300 Win Mag and Sierra bullet (I don't recall the specific bullet, but he thought it was appropriate). The elk eventually got away. He followed the bull quite a ways. He swore he'd never use Sierra bullets again. He switched to Nosler Partitions. He felt that there was little penetration with the Sierra's.
Like you said if the bullet isn't driven to fast, the issue will go away. But if I'm on the prairie or in the mountains and expect up to or more than 300 yards for a shot, I'll probably be carrying a 300 or 338 and if I get a 15 yard opportunity it is too late to switch bullets.
What has worked for me is primarily Interlock bullets from Hornady and Nosler Partitions. I've never had a failure with either of these. I also have not had problems with Remington bullets, but they usually don't shoot as accurate as the Interlock�s and Partitions (as if an extra 1/2" to 1" groups size would make a difference) I have heard from others that Sierras work OK for them - I wish them luck. Personally, I don't want to increase the chance of wounding a game animal, which I think might happen.
I acquired a 264 Win Mag in 1969 and had issues with all of the cup and core bullets I tried then - I didn't try them all, I am sure. I settled on Nosler Partitions (140 grain, if I remember right which were turned on a screw machine) for deer and antelope - never a problem. I didn't have the fortune to try the 264 out on Elk.
I do not understand the Speer bullet failures I've had and I have not experimented with them on game animals after the failures.
Basically I agree with what you've said, and I'm sure you've shot more big game than I. But for some reason we've had some differences on a couple of occassions.
No exit, but all I found was the jacket. The clockwork was pretty well mush. The deer never knew what hit it, but I'm not so sure that would have been the case, had I hit the shoulder bone. 
