Well, my tactics usually depend on whatever I'm trying to achieve. If I'm just delaying another huge Seleucid incursion into Armenia with my border guard, then I'll just fire them up with arrows for as long as possible and retreat when out of arrows/enemy approaches for combat. Usually that's a good way to make some cassualties for the enemy and suffer none yourself (at least if the retreating troops don't go mad and start running around headless >.<)

Since my main battle line is usually composed entirely of Cataphracts and their archer variety, I'll use Byzantine (-ish, I can't recall if they were really Byzantines I was reading about) tactics - let my archers fire at the enemy, then retreat behind the trusty tanks if threatened by arrows or cavalry (although generally the archers will butcher Greek cavalry which Seleucids seem to love so much). Then, when I'm out of arrows, I use CatArchers as bait and beat them to death with my mighty armenian hammer.