If you put five Very Large Strength charms on a weapon, or 5 Very Large Constitution charms on a suit of armour, you've already got a massive advantage over anyone else of your level. I don't have the Charm Weapon skill, so I don't know how much of a bonus charms add. Think of it in character levels. If Very Large Charms give you a +8 bonus to a stat, you could essentially rise 8 character levels by using 5 of them.
And I think that the omission of the Horadric Cube makes charms more interesting and risky to use. No longer do people hold onto every single charm in hopes of one day producing a Mega charm. A charm is worth what it is worth, and they pop up often enough to recharm new weapons and armour that come along. You seem to find (by any means, including trade) about one per level.
