Not that your statement is wrong. But you seem to have an unrealistic expectation of what sort of miracles a tank should be able to pull out of a hat when put into an average DF group.
Fractal has one much harder pull near the middle of the dungeon immediately before the chimera room. Neverreap has two, each before the first and second bosses. In all 3 cases, the difficulty of each are not determined as much by the tank and healer as much as they are by the two primary DPS players. These particular full-pulls can not be sustained at their maximum power for very long, and in most cases the difference between handling it or not is far greater than a few strength-buffed tank attacks. You'll die first.
When your DPS are still working up their Law gear (and that's a lot of them), it can be very hard to survive these pulls without splitting them up unless you have the greatest safety net possible. We can usually tell from earlier fights just how likely these pulls are to work. But it should be a no-brainer which one works out better:
-The DPS can place their AoE on 8 enemies at once while having a slightly weaker tank-dps.
or
-The DPS can only place their AoEs on 4 targets at once while the tank is doing slightly better, often single-target physical damage.
Suddenly the latter case is the one that safe and slow. The former is significantly quicker than any small bit of time you might lose on a single bigger target like a boss (especially that damn minotaur who cuts chunks of your melee time anyway by charging around and occasionally throwing out a 360 degree knockback). If you're rolling a party of veterans sure, but all too often I find that VIT makes impossible pulls possible. And hey, so what if the healer has to cast stronger heals, at least they have more time to act on it. Spare time is DPS time.
And if the healer has more DPS time, they will actually lower the damage we take "by making the fight shorter".