What do you feel about the assault gren doc in 2v2? mechanized assault? Sorry the name escapes if that's wrong.
Assault Grenadiers are still sort of useful. However, they are more likely to die from practically anything since they don't have the same survivability from regular Grenadiers. The only use for them is the sprinting and grenade assault, though the munitions are far more useful elsewhere...
The Panzergrenadier Assault Halftrack is nice in certain cases of hit and run style strategies. However, a the Halftrack is useless since it can't reinforce or have a machine gun. The only good from this call-in is the fact that you can get a Panzergrenadier unit out without teaching to Tier 2. Though it costs a bit of fuel, which is needed for buildings and battle phases.
The Stug III E is good players who have plenty of infantry. Though it must be supported since it is weaker than all the other Ostheer tanks. It can't fight regular tanks that is for sure.
The light artillery barrage is good against static units that can't move fast enough. The best I can see out of this call-in is taking out a player who keeps his anti-tank guns together and doesn't spread them out or units in buildings.
Last, but not least is the Tiger. A good all-around heavy tank that can act as a spearhead unit. I think it's best to keep it supported since it is needed to deal damage with British tanks or tear the Americans apart with the damage it can unleash.