I'm just starting my first campaign... but so far i can't see the point of the following units... can someone enlighten me?

1.gladiator: a half sized infantry that takes 2 turn.... it dies like flies vs any calvary charge... and isn't increidablly great vs much else (it's bonus vs animal... does it work vs horse or just elephant/dog/pig???) why get these guys? a normal infantry tend to work much better...

2.war pig: errr dogs are much better and lower tech.....? why get pig?

3.ballista: while not as horrid as MTW ... still not much better either...

4.The dudes that can hide anywhere (i'm using a chinese version so not too sure bout particular unit names) i never quiete figure out how to use these type of guys in all the TW series... they can hide sure but they get revealed when u get close anyway... not like they can charge fast or anything...

So can ppl enlighten me on the usese of these guys?