The converted mana cost of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was
Its better than Sleep, helps get things killed, life totals dropped, and tapping all of the stuff without vigilance (or that couldnt attack for some reason like Dueling Grounds or having defender.) This is a very strong card with a very strong effect, given that all of the creatures out there will swing, leaving their players open for counterswings
Its still a two-power one-drop, which is exactly what red wants, and honestly, wed play it even if it was just Jackal Pup
Getting both in one card is even better value, even if it is lower tempo
A very useful and versatile spell tacked on to a very easy to cast and hard to kill creature