Sith marauder good replacement for sith empire trooper?

It works good on offense as long as you don't need a pretaunt. For defense, it makes you vulnerable if they have a faster Darth revan or a fast thrawn that will fracture your Darth revan.

I also just reliced mine for papa palps. I may occasionally put him in on defense if my opponent has a slower Darth revan and it looks like they won't be able to out run my Darth revan with a character like thrawn.

My sith empire trooper is only gear 10 though. If you have a relic with empire trooper, it would probably do better on defense than marauder.

You can always use marauder in a left over sith team to clear the garbage teams your opponent leaves. Or in a Darth revan team on offense.