Puzzlebox is actually great on any hero with a longer duration slow (you'll notice people get it on Slither, Hellbringer, Demented Shaman and Wretched Hag, and I even get it on Accursed from time to time ) because it allows your minions to catch up and deal a lot of damage.
With Balphagore, it gives you two minions on top of the standard 5, which is some crazy DPS and pushing power, though I suppose it could be a bit taxing in terms of micro. It's definitely a nobrainer if you're countering invis heroes though.