Which worked because Hearts have two physical, mobile strikers.
They also have good discipline at defending deeply, as on numerous occasions we had two banks of four in front of us. When Djoum/Buaben did drop deep to collect the ball from Alexander, they more often than not sent it long to previously said strikers. If Thistle did that, we'd lose the ball due to not being physical enough up top, then we'd have a man short(in most games) in midfield meaning we'd be overrun, therefore exposing the defence.
A lot of people dislike the one up front tactics but it is a neccessity as we don't have enough quality in midfield to cope with being a body light there.