But what do you expect AC to do? I don't believe that the EU compensation guidelines apply here as it is a non-EU based carrier flying TO the EU (reverse situation it would have applied)

There is no such thing as a 'first class passenger' on AC. If the inbound flight was really 5 hours late in arriving at YVR, the OP had many options to consider, including 2 BA flights, possibly the new Virgin flight, LH, Condor, Edelweiss, Air Berlin, Air Transat etc. Not to mention, he could have flown on AC to YYZ or YUL and connected from there, either to another AC flight or to a partner flight. He may not have enough experience to know how to best handle irregular ops, but it sounds like he also wasn't very proactive in looking at how the delay may impact his onward bookings. He could also have used the long layover in London to find an alternate routing to his destination.

I realise that many travellers are novices, and would in the same situation just sit around and wait, but when so much is at stake, wouldn't most people use that 5 hours time to actually be proactive?

And lounge access? Why? Should AC give lounge access to every single person on that flight at the *A lounge in T1 for the delay? Or access to the already tiny AC arrivals lounge at T3?

In reality, the airline owes the OP nothing. I'm not an AC apologist, but I do find the 10% off offer reasonable.