Kennen's changes were a massive nerf to being played support.

He's been a viable choice for Support for quite some time; years actually. Even played in the lcs a while back. Despite how much people hate him he's has items to fight against him, and his ult can be exhausted in top lane anyways. So why is he bad? His roaming his still strong no? yes and no. He retains the power of his abilities, but what would be a power spike isn't. Here's the data

Damage decreased to 40/75/110 from 80/145/210 AP Ratio decreased to 20% from 40% Reworked effect: Successive maelstrom hits against the same enemy deal an additional 10% damage for each hit they've already suffered from this storm. Enemies hit for the full duration should take roughly equal or increased damage to before, but initial hit 40% lower.

Kennen supports don't get much ap at all. They have limited gold and rely on play making so they need to build tanky, but they will grab a damage item early. the damage nerf is a nerf. and 60% damage at 110 is only 176. He's a play maker and he wants to snowball a lane or his team mate, but without a power spike and his damage getting gated so heavily to get all 6 stacks Which if he can't because of a displacement like alistar knock back or vayne condemn Which even though they were bad for him before the idea of having to hit all 6 or lose all damage with all the magic shields out right now, its sad.

Mise well play Annie Support. Tibbers INITIAL MAGIC DAMAGE: 150 / 275 / 400 (+ 65% AP) and now u have a bear smacking you with aoe damage on top of it.