Put the stacks together
Assuming you can cast him with sufficient protection, that is
Its not painful enough
The -7 is akin to the -12 of Jace, the Mind Sculptor because youll use it after the game is pretty well locked up
This is a strong payoff for hitting your opponent -- something you're going to do in aggro decks pretty naturally
So for example, green could have some variation on Autumn's Veil: Spells you control cant be countered by purple spells this turn, and creatures you control cant be the targets of purple spells this turn. At one point, a purple card was designed like this, according to WotC: 1P Instant Choose one: Counter target green spell, or destroy target green permanent, or destroy target Forest. Purple would hypothetically add four 2-color combinations (WP, UP, BP, RP, GP), though green+purple would be rare since those two colors would be hard enemies