Here is a possible explanation for the 3-hour hold...
Green HYD fails, inducing Yellow HYD overheat as well (thanks, Dg800). Crew depressurise both systems per ECAM, enter convenient hold to plan for immediate landing at LAS on Blue system only.
LDR approx 10,700' from the QRH, longest runway 14,510' so no problem there.
Y HYD cools down, allowing pump to go back on during approach preparation. Crew elect to hold for a short time and see if Y HYD overheats again - it does not so they burn off to MLW and land.