I personaly think this card is fine for now. For you that say this card must be nerfed, what kind of nerf is okay for this card?
I look at some comment that say increasing the cost is the way. Some say if this card cost 6, it will not be used in aggro and I agree.
The problem is that Giggling Inventor can be a great defensive tool for non-agro deck. But if it cost 6, will any deck play this card? Will any control or combo deck still play this card? Bonemare is an example of this. Many deck run this card but after 1 cost increase, the argument that Bonemare would still be a useful at 8 mana is gone. No midrange, tempo or control run this card.
if you think 1 cost increase is okay as nerf, I think you're not seeing a bigger impact. The nerf will nuke this card like it nuke Bonemare until no ones plays it. The nerf this card needs is a slight nerf. IMO making 0/1 Giggling Inventor with the same text is okay as a nerf but not 1 cost increase.