League of Legends (LoL) Question: Udyr pheonix buff

Not really, tiger stance is still more efficient compared to phoenix stance. The damage is usually better and you cant take objectives faster than you can with phoenix.
Phoenix is only really useful for fast wave clears(but tiamat can fix this) or when your against champions that focuses armour(malphite or rammus).

Overall phoenix udyr had a small boost but tiger has gotten a much better boost and is better overall.

You can still run it but its not at a good spot at the moment.