a INT can easily get to 80 with only fire 80 and light at 30. Since if he just max the first fire nuke (needed for last book too) he will have 2 strong nukes (for his level) to use, and 2 nukes is enuf, since they have a very fast cooldown.
This is how i always level my nukers, or i take light and spear and leave spear at 36, or just take fire and leave light at 30. Easy to farm if u already have a tree max
