It does not need DPS....the eye makes it killable by any two champions. You don't even need a tank if you rotate aggro. Herald isn't worth controlling with your duo lane. The dragon is way better than Herald. The support can't roam as efficiently if he's stuck up in top lane. The longer lane makes it easier to gank the ADC. The buff isn't even good on laners because it doesn't make your minions have any extra defense. If you're pushing down their tower with it, you were already crushing the lane and didn't need it. If you're behind in lane it doesn't stop them from shoving waves under your turret and denying you farm. It's better to give it to your jungler for the extra movespeed. More movespeed means faster clears, better invades, and crazy awesome ganks. After you gank and kill the enemy/force him back to base, you can just use the buff to push down his tower while your ally heads back to base. The list of reasons not to send your duo lane top goes on and on.