Here is how to rework dorans shield to fix top lane while keeping it fair for bot lane:
Melee only 80 health 8 health regen Unique: If there are no enemy champions within 600 range for 3 seconds, you gain "Hit and run" Hit and run: For 3 seconds after auto attacking an enemy champion, block 40 damage from auto attacks and grant 20% movement speed while moving away from enemy champions.
EDIT (in case its too oppressive bot lane) @WoonStruck
Unique: If there are no enemy champions within 600 range for 3 seconds, you gain "Hit and run"
Hit and run: For 3 seconds after auto attacking an enemy champion, block 40 damage from auto attacks and grant 20% movement speed while moving away from enemy champions.
EDIT (in case its still too oppressive bot lane)
Unique: If there are no enemy champions within 600 range for 3 seconds, you gain "Hit and run"
Hit and run: For 3 seconds after auto attacking an enemy champion, block 40 damage from auto attacks from that champion and grant 20% movement speed while moving away from enemy champions.
The counterplay to this item is to not let the enemy fight in short bouts, when they go in, try to extend the fight to marginalize the effect of hit and run. Generally this can't really be done if the enemy is under tower.
This covers the weakness that melee champions have when trying to farm under tower versus ranged champions, because it gives the melee champion a way to exert some threat. They can engage for a winning attack trade and then clean up the minions, rather than constantly take auto attack damage for free.
It also makes a good "i'm losing" item buy, because it protects you from tower dives.