Does anyone have any thoughts as to tactics with a post-Marian army? Thing is you're no longer bound by the triplex acies and can deploy in as many lines as you like. But that also means there's no immediately obvious deployment strategy either.

I've been experimenting with the above two-legion force against overwhelming numbers, and they haven't performed too well when I haven't bumped up their experience a fair bit. Most recently I got narrowly defeated by a huge Gallic force (I killed a lot more of them than they did of mine, but eventually their greater numbers counted morale-wise).

I've tended to use a staggered single line, with spearmen on the flanks. But being outnumbered I often get rolled up on one flank, or find nothing happening in the centre and am forced to split my army in two.

Does anyone have some useful deployment/tactics against:
"barbarians"
desert peoples
horse-archers
"civilised" armies