After watching your video GoogleFrog I realise that pathfinding in this game will never be ok when there are a lot of units on the map. Is this one of the reasons we get lag on larger maps ?

I were mostly annoyed by the scorcher.
I were trying to skim the edge of hill but I gave a command just slightly outside the pathable area and the Scorcher stopped.
You could put the blame on me for trying to move outside a pathable area, but I think it is reasonable that the unit should have tried to go to the closest point in that situation.
The con starting to reclaim is mostly on me though

But maybe I want it to move to the closest pathable position.

This may be tangential but i also very much dislike that whenever i issue an order onto unpathable terrain, the units which those orders have been issued to simply stop, often incomprehensibly so in the heat of the moment.

I can think of two non-mutually-exclusive things that could alleviate that:

1) Feedback on orders which will not be executed. Possibly audio, but also some kind of a red X instead of the usual expanding circles click-ack would be good.

2) Such orders being blocked before being sent. That is, clicking unpathable terrain does nothing to the unit's order queue while the current behaviour is pretty much equivalent to Stop.

There's a reason ZK got rid of the default Wait keybind, and Accidental Stop seems a lot like that.

It did 8 days ago!

Good riddance, then :)