I believe she can still be used at 2* level, but I think it's recommended if you have her at 3* for the dodge passive.

Personally, I run her in arena as the Water main with Fubuki (for that no cost, high combo mystery) and Edo Haku (barrier if you own the initiative advantage, also cuz Acupuncture). I'd use Darui...but I don't have him. My team usually looks like this:

x - x - x
E.Haku - Fubuki - x
x - Water main - Guren

Healing jutsu for both mystery and standard, Shark Bomb chase, Healing Tips (usually), Poison Tai and that goes with the Rhino summon (plus Pakkun summon mystery).

Combo usually goes (assuming things go off correctly): Guren low float - Guren drain - Rhino #1 - Shark - Guren drain #2 - Rhino #2 - Haku Acupuncture - Fubuki high float and tag.

Oh really?