Runeglave some quick thoughts
Right now everyone agree's it's weak, I don't play AP junglers or jungle at all, so I'm not going to debate one way or the other, all I will say is I'd rather an item be a little underpowered than a little over powered.
What I can do is give a solution for a good way to buff it: make it deal 100% of your AD, rather than 75%. Right now in many cases it's damage is no better than a sheen, and in some cases worse than a base sheen. This should never happen, AP junglers invest a lot of weakness into the early clears, they need to get some pay off from it. Upgrading your item only to have it deal less damage is a kick in the balls, a player should never have to worry about this. I'd go as far saying regardless of it is op it should be changed.
That's all the time I have, see ya.