But this "imperfect information is still very valuable, in its state now its a way for a laner to buy 4 of them and whenever they see a ping back off, then go back to farming. It seems like its a more efficient than a ward because of the cost, and the downside it has won't effect you while you are trying to lane.
Imperfect information is tremendously valuable. Absolutely agree with you there.
I also agree with you that protecting your lane with these is pretty easy. However, I'm fascinated by the possibilty space that this results in:
For example:
If people use Sight Wards to gain safety for their lane - the lane has perfect information in some avenues and is blind in others.
If people use Mandrakes to gain safety in their lane - the lane has imperfect information in most avenues.
However, in scenario #1 - The only options available to junglers to really interact with lanes happen if the jungler is at full health.
When scenario #2 is in force - junglers who are at half health or quarter health can make threatening 'bluffs' that are just as effective without compromising their clears - due to the fact that the Mandrake won't reveal their health status or direction that they're heading in.
So, while it gives you adequate protection against full health junglers - junglers have a much easier time scaring you and forcing you to play passive if you rely on the cheapness of the ward.
When this is the case - we might see more flexible jungle and couterjungle patterns due to the fact that the jungler being 'spotted' in the early game merely freezes lanes rather than invite instant retaliation if they're low.
That said, it's not guaranteed that any of the above will happen of course - it's just a possibility space that I'm interested in experimenting in - I don't really care if Mandrake makes it through or not - but I do want to see what the more imperfect information models do to the range of actions. (It's a little difficult because it's subtle.)