Ursa is a gimmick pick, but unlike with brood, has very poor late game. I feel this is why he wasn't picked at TI9 due to being an all in early/mid game hero. He used to be a standard anti-carry, but with so many buffs to other carries, no one really has an Ursa issue anymore.

In order to make him viable again, having a high level talent or scepter enabling his ult to grant one of the following effects should easily make him viable (and imo balanced):

a) Illusions attacking Ursa while enraged die instantly

or

b) Enrage has charges (3)

The main counter to ursa is control or illusions. His aoe damage capabilities are almost 0 and when it comes to being kited without an aegis, he has the option to blow up 1 hero before becoming fish food. The above options would counter these issues, and having a high level talent or costly scepter would prevent him from obtaining this too early.