A better offensive ability defeats the "support" genre he fits in to. Also, his E when combined with Daisy is very useful and important. Not just because of the slow, but because I often tank towers and objectives with it, and it helps so much. It's low CD means I get it up quite often, but the low duration means it doesn't tank as much as other shields and is more timing dependent. I have saved PLENTY of lives with that E, including my own, peeled like crazy thanks to the slow proc, and of course used it to help Daisy land her knock up.
There is nothing about that Shield that makes it worthless, lackluster maybe, but still incredibly useful. While adding better scaling might help, I am curious as to whether you can synergise it with the AS buffs that some items grant shields. It would help Daisy land her knocks ups even more :/
As for the OP, if you can't think of other ways to use Daisy (though tanking objectives is also good) than you probably don't play tanks often, because you use her the EXACT SAME WAY. Peel, damage soaking, and CC. If the enemy dodges the cc, it means that they are being forced away from you, to which you can land your other abilities or focus someone else.
I have been winning more with her, and still learning new tricks. I once ganked top lane from two sides at once. I came from behind so he ran towards the jungle brush where Daisy was waiting, and with my top laner behind him, he was completely trapped. He couldn't run passed daisy without taking at least one knock up, then he was rooted, and then slowed and that helps land another knock up. Not to mention the top laner interaction. Same can be done mid, you can actually hide daisy in one brush, walk to other and then gank from both sides. The creative application is endless. Once they fix her bugs, she will get much stronger