The problem is a creature with a good ability can't be too cheap, or it can't have too high of an attack. That means in the end you're really not buffing it. You're taking away something of life's trademark, the rush, to replace it with control. That may not be a bad thing, but I think it's part of the charm you can cough up 12 attackers for almost nothing.
: Peck - Deal 1 damage to target creature.
This may not be so bad, question is if there needs to be a cost increase. If so, it would miss the point. Also, would you really go with mark of
over this? It's only 1 damage and even slower than poison. Recall the unupped toadfish that can be used without the ability. You see the same thing, but worse, with pest and antlion. I'm no real fan of these marginal abilities. If the creature has it, make it worth while so people will play it. (For example in a duo or with life pillars and another mark.) If people want to rush, also give them a chance to use a mono with two plain attackers.