I took a little step back from the game the last couple days to play other games and have only played Crait a couple times.
I thought I saw first order walkers during the initial assault but now that you say something they were behind the fight so now I'm wondering if they were actually being pilots or just a visual prop.
Those speeders were pretty tough to deal with. I spent most of the first part of the match with ion turret and sentry rolling just trying to keep them honest. Would be nice if there were some more tools to deal with them. Maybe I'll try ion shot, would be pretty lol-worthy if they could be taken out with that.