Imbue.

Im playing full int spear. My question is about imbue. I should max fire or light imbue?

Fire has a higher damage output than lightning, but as a pure INT, I always go Cold/Lightning, which leaves me the lightning imbue.

But now fire cold light is one mastery, so i can go heuks and all these 3.

That's something completely different, lightning imbue has a transfer (not sure if 2 or 3), so it's more like an AoE imbue but with less damage. Fire has a greater damage output, and you put the mob on burn status which adds also a good amount of damage.

So it's basically up to you, what you more prefer.