If all goes according to plan, I never bother to increase my heroes' personal strength. Command, -1 enemy stack and stack critical strike are much more desirable options.
Occasionally my hero will wind up alone and vulnerable after an unexpectedly close battle, and only then do I bother to increase their strength.
Beta 4 doesn't seem to address this issue. Ruins will be fought with undead lore, not strength... so, there won't be any more incentive to boost strength than there is now.
Here is a unit I thought up, that would terrify puny heroes everywhere....the assassin.
This incarnation of the assassin bears little resemblance to the DLR version (which had critical strike). My conceptual assassin would be a dedicated hero hunter.
The assassin would have the 'assassination' ability. This ability would allow it to ignore fight order to attack an enemy hero (if one is present). So, when the assassin gets its turn at bat (during a battle) it immediately goes for the opposing hero's throat. The hero fights back as normal. Once all assassins (or opposing heroes) are killed, fight order returns to normal.
The assassin would need to be quite weak and take some time to produce..probably 3 turns.
Assassination could also be a skill available to a rogue type hero.