Duskblade needs a cooldown, all champs in the game should get more natural mr

For what duskblade does for how much it costs and how much it gives, it shouldn't have 0 cooldown on the damage. It's ridiculous. What's more, almost every game, you see AP mids or sometimes supports go straight sorcs into mask because it ignores 100% of any ADC or mid lane champs' resistances which is ridiculous and its almost the same price as duskblade. There is seriously too much free damage in the game.