FWIW I operated into EZE last week from GRU (that's probably blown my cover). ATC was applying slot times to flights ex GRU/GIG to EZE, and subsequently 10 minute spacing between aircraft on entry to the EZE "FIR". The weather (fortunately) was CAVOK "plus" so we were offered (and took) a visual approach from over the City. From past experience EZE tends to be a either a visual let down or in poor weather they revert to procedural let downs, even with radar.
As to Heathrow Director's comments regarding EZE being busy or not - it's not the busiest airport in the World but there seems to be a bunching of longhaul arrivals around 8-9 AM as the Longhaul stuff comes in, shuttling from GIG/GRU or direct from the States.