Wow. Have I learned my lesson.
I just completed the single player Mating Season quest (Hunt Rathian and Rathalos). The first time I use my default weapon, Blazing Falchion (SnS 238/440 fire), and I time out as Rathalos lands in my pitfall trap. The second time I use Cataclysm Blade (GS 768/450 water), and I finish in under 20 minutes.
Always bring the right weapon to battle.
(Is there a trick to hitting the raths with a sword and shield? They stand so high up from the ground sometimes. And it's hard to knock them from the air even with a jumping attack. When I used Jhen's long sword, I always smiled when rathalos fell from the air after two overhead X attacks.)