I run two land speeders with multi meltas and heavy flamers and they work well; though they do act as suicide units and are quickly targetted. A typhoon can hang back and fire kraks, but a long range A.T weapon like a lascannon can still easily take it out.
As for a predator currently I am running autocannon, heavy bolters and a storm bolter. It has good anti infantry but I found it a bit wishy-washy about scoring kills. The reason for the storm bolter is so I have two weapons to fire when I move. Consider it's anti infantry I didn't think it reaped loads of kills. I am however thinking of taking autocannon and lascannons for anti tank, the autocannon isn't great but the lascannons will give me some long range anti tank. However I wouldn't mix a lascannon and heavy bolters as one is a anti tank weapon and the other anti infantry, they do not mesh well.