The reason to do it like this iso a conventional tail is stiffness / weight and more importantly: noise. The tail area deflects a lot of noise above populated areas, probably allowing airlines to fly more to noise restricted airports. Airbus and Boeing have both been experimenting with it for years.. Aircraft like the A10, YF-23 and An225 have similar tail configurations..
An-225 has H-tail in order not to have fin or rudder blanked by external load. The same reason 747 Shuttle Carrier has extra fins and rudders at the ends of tailplane.
Several other airplanes have H-tails in order to limit the total height - like Electra.
As for noise, I think B-2 has engines over main wing to suppress noise. But your jet blast would interact with the wing lift, like it does on An-72/74.
However, upper surface blowing has another problem. When one engine fails, suddenly you have asymmatric loss of lift in addition to asymmetric loss of thrust.
And if you blow your blast over tailplane? Huge upper surface blowing forces far from your pitch axis! When a tail engine fails, the plane would drop tail due to loss of upper surface blowing...