Flamers are your friend ;) Ofcourse my sisters have plenty of those. I once played against orc speed freaks in a tourney. My cannonness blocked a couple of trukks coming from the flank, and my calidus held up some with her neural scrambler and then the orks when he got out.
Flamers did wonders against his orcs and my seraphim chopped up his little trukk with ease with their eviscerator.
Small note: Speed freaks when they fall back, go to their trukks and auto regroup in them. So if you shoot a squad that just disembarked and it runs back inside, assault the trukk they are in. This is considered part of their unit, so you may assault it.
( that is how the judge ruled it on that tourney anyway )