Goldenrivette
Before I answer your question, in support of my post I will quote from IFALPA(ICAO) document you referred.
4.3.7.2 The pilot-in-command shall continually ensure that the amount of usable fuel remaining on board is not less than the fuel required to proceed to an aerodrome where a safe landing can be made with the planned final reserve fuel remaining upon landing.
So the moment you discover you only have 5minutes reserve instead of 30min you have to land back otherwise you violate this. What happens at destination won't save you. On takeoff you are supposed to be go minded and not in the air. Now coming to your question. Do a FORDEC and see for yourself. With further delay which cuts into alt+reserve regulation wise you should divert. Because if you are delayed still further or forced to divert later due to unforeseen events then you will land much short of regulatory minimum.
Last edited by vilas; 13th May 2018 at 13:10.
Reason: correction