Originally Posted by Crimson5pheonix
AD's SHOULD be building damage first anyway. AS is late game, way after laning phase has ended. AD's that build AS beyond zerker greaves are doing nothing fast. THAT'S why Nunu is a bad support, the only thing he's good for isn't useful until after laning phase.
Okay, I'll disagree with the original OP, but I'm well aware of the power of Nunu support (Gosu Pepper + Genja Nunu/Ashe lane). Give great MS and AS to your carry and they gain great kiting power in simply firing a shot and running away.
If you've ever seen Genja play Ashe, he'd often rush Zeal and a couple Doran's blades for simple ability to kite the **** out of his opponents. Building AS during the laning phase is viable if you know how to use it. Given the fact that many players simply don't know how to properly use it, I can understand your opinion.
However, you did touch upon something very important: Nunu is a lategame support. He tanks and powers up ADs such as Kog'Maw or Vayne and turns them into monsters without heavy AS investment on their parts. He slows down the AS of the enemy ADC and bruiser, plus draws CC using a great big AoE slow. He's by no means weak, but he does rely on getting levels and items (and his ADC getting them) to really shine.