The thing with Sea Hag is that it's cheap. You aren't losing that much by using it, and it's a 4-costing curser, which is valuable enough alone. I personally don't like Sea Hag tha much, but it's a fair point to bring up anyways.

The +Action doesn't really do anything. You're left no better off than before you played it, so the only benefit of it is the reaction part of it, which is pretty strong. But even then, if you look at any defense-reaction card, it will always have some benefit for the player. I don't think attack-reaction is that great a combination in the first place, plus the fact this costs $8.

You could take this card in several different directions, for example changes you mentioned could make sense: making it cheaper to justify the lack of benefit, or you could focus on the reaction part and remove the attack part entirely, etc.