Guinsoo's Rageblade is 68.57% gold efficient with no stacks.

#reaching 192.2% gold efficiency at 8 stacks, without its area of effect.

So it's balanced as long as you _make sure they don't land autos. _

#All you've gotta do is:

Be Teemo, Jax, Pantheon, AND Shen (Jax being the biggest offender of this item in the first place) at the same time.

And go back in time to season 1, buy some Ninja tabi for the dodge chance, then come back. I'm pretty sure you can do this with Zilean.

EDIT: Oh, nevermind. They're generated on-attack, not on-hit. So the only way to prevent them is to focus the fighter instead of the enemy assassin with your hard CC, so your team dies either way. Thank you to the commentor who pointed this out.