While I've made no shortage of jokes about how fragile the Galaxy class is over the years (seriously, just look at how close the D's warp core comes to breaching throughout TNG's run) it should be noted, only three are confirmed destroyed, and those three all have extenuating circumstances. The Yamato fell victim to an alien computer virus, the Odyssey got rammed by another ship and the D was fighting an enemy that had visual access into the engine room during the battle.
That said, some of the alternate destructions of the D are rather questionable. Like the Bozeman clipping a nacelle causes the ship to spin uncontrollably until it explodes. Or in Parallels, the Enterprise from the Borg conquered reality get a phaser hit in the middle of the saucer section and that somehow triggers a warp core breach. Even taking into account that ship would have been in poor shape from three or four years fighting the Borg, that still doesn't make sense.
