Calculating Gravitation
There are a few ways to calculate gravitation. First things first we need to make ourselves clear that for our purposes gravitation is nothing more than a force that causes acceleration. One way to calculate acceleration is with the formula F = m * a. We don't know the weight or mass of our character nor if different races and character sizes play a role. Thus we need a different way. Another option would be
a = Δv / t. For this formula, we only need the velocity and the time. To get the velocity we can use the formula v = d * t. We can get the distance d using ingame measurements. For the time we can use a mobile phone or some other way to use a stopwatch. To get the velocity delta we need two spots, one with a long fall and one with a shorter fall or one that is long enough to perform two calculations on it.
a = Δv / t. For this formula, we only need the velocity and the time. To get the velocity we can use the formula v = d * t. We can get the distance d using ingame measurements. For the time we can use a mobile phone or some other way to use a stopwatch. To get the velocity delta we need two spots, one with a long fall and one with a shorter fall or one that is long enough to perform two calculations on it.
Finding the Right Spot
An ideal spot would feature the following attributes:
 vertical wall
 nothing in the way during the fall
 easy to measure
I've decided to scout Divinity's Reach for spots and have decided for the one at the Plaza of Kormir and the other one is further up the Kormir High Road.
Guild Wars 2 Screenshot: Fall distance at Plaza of Kormir 
Guild Wars 2 Screenshot: Fall at the Kormir High Road 
Measuring the Walls
Guild Wars 2 Screenshot: Measuring Concept, Plaza of Kormir 
shades which feature a 180 unit radius and the staff trap skills which feature a 240 unit radius instead. Doing some experimentation I figured out that the indicator of the Summon Meat Scepter er... Flesh Worm has a 60 units radius.
The second wall doesn't fit into a picture and was much harder to measure due to the marks disappearing after a certain time. It was 5 marks high and a little bit more than the Summon Flesh Worm indicator. This makes a distance of 480 * 5 + 120 + λ. For my calculations, I've set λ to 15. This gives me a distance of 480 * 5 + 120 + 15 = 2535 units.
Thought Process
If Tyria has gravity, the velocity at the longer fall should be higher than the velocity at the shorter fall. Both drops have a distance delta of 2535  883 = 1652 units.
Possible Outcomes Include
a) The velocity of the first drop is significantly lower than the velocity of the longer second drop.
In this case there is an acceleration thus enabling us to further research. When we would do calculations on another planet or place in real life this would be the obvious result. In the case of game development games may not necessarily have acceleration and use a fixed fall speed.
b) The velocity of the first drop and the velocity of the longer second drop are similar enough.
There may always be errors in these empirical calculations. Errors during measurement specifically. Nonetheless if they're equal enough this means the falling speed is constant and the acceleration is strong enough to reach the terminal velocity in an instant.c) The velocity of the first drop is significantly higher than the velocity of the longer second drop.
Honestly, I have no idea what's going on if this would be the case.
Measuring the Fall
All we have to do at this point is to place our character, prepare the stopwatch and throw ourselves into our demise. Don't forget to start the stopwatch when the character starts to fall.Due to the high chance of errors from reaction time I made 10 attempts. This table features all attempts and their resulting velocity in units.
Measurement  Short Drop (883 units)  Velocity (883 units)  Long Drop (2535 units)  Velocity (2535 units) 
1.

0.97s

910.31u/s

2.51s

1009.96u/s

2.

0.91s
 970.33u/s 
2.39s
 1060.67u/s 
3.

0.97s
 910.31u/s 
2.53s
 1001.98u/s 
4.

0.87s
 1014.94u/s 
2.67s
 949.44u/s 
5.

0.88s
 1076.83u/s 
2.66s
 953.01u/s 
6.

0.82s
 939.46u/s 
2.62s
 967.56u/s 
7.

0.93s
 949.46u/s 
2.56s
 990.23u/s 
8.

0.96s
 919.79u/s 
2.67s
 949.44u/s 
9.

0.90s
 981.11u/s 
2.51s
 1009.96u/s 
10.

0.85s
 1038.82u/s 
2.61s
 971.26u/s 
Next up we take the average of the velocity which is 973.84u/s for 883 units and 986.35u/s for 2535 units. Now let's convert them to values that tell us more. For this, I'm using the same conversion I've used in all my posts. (1 unit = 2.52cm; 1 unit = 0.083ft)
883 unit velocity is
 973.84u/s * 2.52cm/u = 2454.08cm/s which is 2454.08cm/s / 100 = 24.54m/s
 973.84u/s * 0.083ft/u = 80.83ft/s
 986.35u/s * 2.52cm/u = 2485.60cm/s which is 2485.60cm/s / 100 = 24.86m/s
 986.35u/s * 0.083ft = 81.87ft/s.
Conclusion
I'm gonna call it a day here. The values seem to fall into either case a or case b. Now the question is whether or not it's a measurement error or if there is gravitation. Though if there is gravitation we can calculate it by finding a drop that's high enough on which we can do two separate time stops at two different points. That sounds difficult but it might work and even easier if done on video. So I'm gonna look into that in the next days. Until then.. stay tuned and maybe you find something else from me that's interesting. ^^