I actually passed N2 with just Tobira under my belt…
Disclaimer: Although Tobira was my main textbook for studying, I had already lived in Japan for 5 years (albeit in an English bubble) when I took the N2 and I have an abnormal penchant for standardized tests (to the level that the SAT’s got me a full ride scholarship). I also studied the book exhaustively, which means I memorized every word and kanji written in it.
That being said, I absolutely adore Tobira as a textbook and almost felt regretful when I finished it. It taught me a lot of useful stuff that I could immediately apply to my life in Japan.
I used Memrise and Skritter to learn the vocab/kanji and then I met with a private tutor once a week to read through the passages and practice the speaking prompts. I didn’t do anything to nurture my listening or grammar. Living in Japan took care of the listening, but my grammar was basically still at Genki 1 level.
Now that I’ve discovered Bunpro, I ‘m retroactively studying all the Tobira grammar and I love how much it’s helping my Japanese.
At this point, I’ve covered almost all of the grammar in the Tobira path with just 41 more grammar points to go.
EDIT: I just finished adding all the grammar points. Tobira covers 128/217 of N3 and 43/210 of N2. I skipped one point in ch 11 and one in ch 13 as they didn’t match the grammar being taught in the book.
TLDR: Tobira doesn’t cover all N3 grammar, but it’ll cover a little more than half and will give you a great foundation of vocab. and kanji on top of it. Definitely nothing to scoff at, but if you suffer from test anxiety or tend to perform poorly under pressure, I’d recommend you use Shinkanzen Master or something to fill in the gaps.