Shizune has no attack, her normal attack is her heal. Best offensive healer is Karin, she can attack and has 2 chases also poison mystery.

Also just do add on, Shizune and Sakura have completely different chases, they don't work in same team, it will depend on what other characters you use.

Sakura goes good with original team 7, as long as you upgrade Naruto and Sasuke to 3 stars, it's a decent enough team to use even into high levels.

Shizune would go well with Hinata/Sasuke, normaly people use Karin here, but they have exact same chase.

Karin is full attack, Kabuto is full defense, whichever you think you need more, they have same chase and fit same teams.