Hey-
After looking over the code it appears that there are actually two versions of AHUD::DrawText. One of them draws based on the center while the other draws based on the top-left corner.
This version (which is the only version available to Blueprints) will draw from the top-left:
void DrawText(const FString& Text, FLinearColor TextColor, float ScreenX, float ScreenY, UFont* Font=NULL, float Scale=1.f, bool bScalePosition=false);
This version will draw from the centre:
void DrawText(const FString& Text, FVector2D Position, UFont* TextFont, FVector2D FontScale, FColor TextColor);
I am still investigating what the different uses of these functions are, however you should be able to use the one that best suits your needs.
Cheers