Heavies - canon food
Heavies from Titan are still weak and can practically be ignored most of the time. Fast units can kill them relatively easily, ranged units can be used against them and art. naturally too. You can't go really wrong when using something against them except champions and themselves.
Art. - nightmare fuel
Art. is quite a scary enemy, though abyssal gliders can just ignore them. Other decent counter is SAT art. like in OF: just take them out before they can return the favour, be careful for hostile flying units.
Range - situational threat
Range units are a substantial threat depending on what you're using. Best counter are fast units (shame the SAT one got nerfed). From my encounters they're faster than SAT art. another decent counter are other ranged units but when facing hostile art. take them out first, beware of hostile fast units and potentially the light units.
Light - sticky
Light units' buffed range makes them somewhat dangerous-ish in some cases, due to their speed. Though fast units shouldn't have too much trouble with them. Despite their force field.
Fast - situational threat
Fast units of SAT are... weird, their range is nerfed making them difficult to use. Though they're faster than SAJM fast units. Best counter imo are other fast units in larger numbers and particularly when hostile art. is on the board. Otherwise range units + art. teams could be reasonable able to tackle them in some cases.
For the campaign map, imo the best units to pick are:
Abyssal gliders + sometimes SAT fast????
SAT art.
Range
For general purpose I agreed with @
-ScytheNinjAlin- , fast units are the best of this age. The biggest problem are hostile art. preventing most other units to be meaningful on the field. Mortar + keen eye is simple to overwhelmingly over kill