[Targetting - 6.63] Mana Burn
Since 6.63, Mana Burn burns mana off the target unit by 4x its current Intelligence, I suggest removing the ability to target non-hero units, at the very least.
If you target a Necromancer, neutral creep, or so forth, you waste your mana, cooldown, and do absolutely nothing to it.
By making Mana Burn only able to target heroes, you can save people from a stupid function (what's the point? it only offers misclicks for players or dumb attempts by newbs who don't know how it works). After all, you can't use something like Doom Bringer's Devour on heroes and have no effect occur.