This route from Napier to Gisborne tries to avoid SH2 where possible. However, there is no alternative for the 70 km from Tutira to Wairoa.
1.) Napier to Wairoa (via. Waikoau and SH2)
2.) Wairoa to Gisborne along Tinironto road
beware: there is nothing in between (take plenty of food and water)