Suggestion for an item to replace DFG

Item name: Not Deathfire Grasp

Stats: 120 Ability Power 8% movement speed

Active: Unique: Applies the debuff Doom to the target. 90 second cooldown. Doom reduces the target's magic resist by 15% for 8 seconds, and deals magic damage equal to 2% of the target's maximum health every second for the duration of the debuff. (total 16% max hp over 8 seconds)

Total Cost: 3100g Recipe: Needlessly Large Rod + Aether Wisp + 650g

Deathfire Grasp was intended to be an anti-tank item, but it was poorly designed for that. A magic resist reduction debuff is much better than straight damage amplification because it will be more effective against enemy champions who are building a lot of magic resist, and less effective against champions who are not stacking magic resist. Reducing the strength of the active effect and increasing the duration to compensate makes it easier for an entire team to capitalize on the window of vulnerability created, and will not significantly increase the burst damage of a single person who uses it before their ability combo. If the enemy team has a strong front line, the kind of situation where you would have to kill their tanks first because you cannot get to their back line, the movement speed helps you kite them backwards. There also aren't very many items that build out of Aether Wisp.

This is my idea of what kind of item could fill the gap left by Deathfire Grasp without providing a champion extra burst against non tank targets.