dude, dagger can backstab good players only once, Shadow Step backstab.. if you know how to play, u dont get backstab again, and yeah, 2,5k backstab is tottaly normal, it should be even more, since in pvp servers whit Max +15, mages has 12k HP, cuz enchanted armor gives like +4k hp full +12 So...
COV, +4 CON etc.