They are now Spine, and Spore colonies and have been instead been bred to serve as mobile defense emplacements.
Also, Ork Boyz squads totally come with burnahs ANYTIME they face nid squads, or any massed faction.
I'd hazard burnahs, and shootahs would be the standard issue for any savvy warboss.
As for defenses, part of the ork mentality revolves around "Boss Poles" so I'd imagine they'd follow standard doctrine of setting up an orky camp the moment they cleared their landing zone.
There's still the issue of Looted siege tanks, valkyries, and battle cruisers that haven't been addressed. Valkyries were to the point in Brood War were even like, 7 of them gave you the air against squads of 20-30 mutalisks.