There's definitely no need to watch all of S2 unless you really
want to. Just be sure to check out "Dead Stop" (easily one of the show's top five) , "A Night in Sickbay", "Singularity" (optional), "The Catwalk", "Stigma", "Cogenitor" and "Regeneration". Though if you do watch S3, might as well add "The Expanse".
... I remember watching "Shockwave, pt. 2" and the Smallville
second-season premiere rather close to each other. The quality gap was pretty embarassing for ol' Team Trek