The Dodgers dominated the offseason with a $1.2-billion spending spree that included the acquisitions of two-way star Shohei Ohtani and pitchers Yoshinobu Yamamoto and Tyler Glasnow, but the three other division contenders didn’t exactly sit on their hands all winter, and they’re not about to raise a white flag this spring. Arizona’s rotation, led by Zac Gallen and Merrill Kelly, …