The idea is a good one, but given how much crap currently drops, you would need to increase those percentages a LOT.
For example, "+5% chance to get dexterity on items"
This would make no difference at all in the game because 1 out of 20 is pretty low, and when you do get that, it'll still be like +30 dex on some super crappy item.
Change that to be "+50% chance to get dexterity on items and dexterity stats are rolled +50% better" then we are talking.
In a perfect world, they would ditch the four gem they have and introduce like 20 gems with all sorts of interesting attributes/stats all over them. Then introduce some sort of new item where you can socket gems into it and it will force items to roll more similar to the types of gems socketed in it. Or something like that :)
Regardless, good idea here, and if these were more powerful, would get me to play more often I think
Well, the system could become even more complex. Each skill could have different levels and the more you would use a skill the better it would become (for example +5% chance to get dex items could be lvl 1, and lvl 2 would bet 10% chance, etc...).
Or the system could be linked to a new "crafting" profession and each level of the skills would be learned with dropped recipes a little like jewelry recipes.
But I doubt the developpers wish the game to become so "complex". They wouldn't make an auxiliary system more complex than the main skill system.