Guild Wars 2

Running the Grenadier trait I should be throwing 3 grenades at once, but on many objects if I throw a grenade at them in an upward trajectory I only throw one grenade.

In the first screenshot, I have targeted the ground, and have thrown three grenades.
In the second, I have targeted high up on the wall, and have only thrown one grenade.

At certain angles, I believe all 3 grenades travel on the exact same path.

Da Sonic.6521:

At certain angles, I believe all 3 grenades travel on the exact same path.

Certain angles and target surfaces. Surfaces which cause grenades to clump together will also cause things like elementalist’s Meteor Shower to drop all the metors on a single spot.

The best way to test this would be to do so against an actual target. Your combat log should indicate how many hits registered.