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I'm basing my definitions of what a demo and a beta are on how they differentiate from each other on a practical basis. Wikipedia isn't an authority here.
Three days of testing will only show the most obvious of errors while allowing a lot of balance issues and bugs pass by. This will, more than likely, have huge repercutions on the Arcanist class, as people won't have enough time to test it properly.
The main purpose for this open beta is evidently to act as a publicity stunt and probably to test stress on the servers. Any actual testing of gameplay is just an added bonus. So it's really a demo.
Three days of testing will only show the most obvious of errors while allowing a lot of balance issues and bugs pass by. This will, more than likely, have huge repercutions on the Arcanist class, as people won't have enough time to test it properly.
The main purpose for this open beta is evidently to act as a publicity stunt and probably to test stress on the servers. Any actual testing of gameplay is just an added bonus. So it's really a demo.