My home airport is YEG and it usually works pretty well. There are a couple of Z1/2 signs around I think but Z1 usually has a dedicated line and it's policed at least to some extent. YYZ domestic has been alright for me (with the exception of the lack of space - GA kicked a bunch of Z3 pax back from the gate and re-announced Z1 only on my last flight from there on Monday); YYZ E gates are a mess as has already been stated.

I had what was probably one of the worst boarding experiences I've had in a while in VIE. They sent all connecting passengers to a service desk two gates away for a docs check right as they were announcing boarding (the sticker was never even looked at afterwards). The Z1/2 mixed sign was in a pretty random place adjacent to the main boarding lines and outside the roped boarding area with no staff even monitoring it. Z3/4/5 were flowing through en masse with no order with a bunch of pax milling around Z1/2 sign not knowing where to go. Had to eventually waive over one of the GAs as she was walking around, point to the number of Z1 people and she begrudgingly opened the rope to let us all move towards the scanning gates. It was pretty atrocious (and then followed by the most indifferent AC crew I've had this year but that's a different story).

This shouldn't be rocket science. I cannot understand why it's so difficult for AC to enforce boarding consistency across stations.