Anyone else feel like Gangplank's ult feels weak under new runes?

Title

This isn't saying he is weak, perhaps it is even best this way as he reaches full cdr and itemization very quickly, but the main damage from his ult used to be Thunderlords and now I cant even finish off a low health champ with it anymore.

Perhaps I am just not using the right runes as well so feel free to say suggestions.