One of the biggest advantages the Black Templar have is their numbers. To get as many marines and noephytes across the board and to your objectives you want to use transports with a large troop capacity.
If you really want to use a Razorback, you could use them as transports for devastator squads. Then you have 4 heavy weapons plus what ever you put on the Razorback. This maximizes firepower for the unit and if need be provides cover for your unit to fall behind until they can make thir move.
One of the biggest things to remeber in this game is that it doesn't matter what kind of tank it is, it will attract alot of fire. Due to this issue, you may want to be especially observant to you opponents and figure out what they go for, then adjust your strategy in future games. I field empty transports alot because people will do there best to kill it, while the squad marches into the objective from the opposite side.