I can imagine +70 spirit is enough to solo grind. The reason I went for 150 (+125ish) is for the cleave grind.
Side note, getting pst 150 total spirit started getting really hard and generally I needed to start stacking survivability.
Finding plate gear of the whale on the AH is big.
Getting the SUPER LUCKY ZF plate gloves of the whale (blue gloves with attack power + of the X) was crazy lucky.
You mentioned getting only two ticks of regen between mobs. That’s why I suggest just keeping the one set of gear while questing. Even if you’re running with 14 slot bags, missing out on one tick of spirit regen is big when it only takes two to heal you up.
Keep your Str/agi gear in the bank for instancing.