The drawback is actually an advantage alongside a Mentor-type effect since it'll keep triggering it.
That is situational though. If you cast Karak, go to case a spell, they bolt Karak in response and you lose the flip you really just got killed on tempo. Him getting bolted out is always a threat but with the few of these cards all that will happen in the worse case scenario is Storm count+1.
I think the interaction with Mindbreak trap and MM is actually really strong and you would likely want to use them over any traditional counter magic, and I could see a list that wanted to run bolts and somelight disruption and just go face. Pyromancer seems fine, I think Mentor and splashing white at that point seems win more since you cannot protect it with FOW as you normally would be able to.
Not sure what other purely free spells there are that are worth exploring. Mogg Salvage could be a thing.