Were not the Askari used by the Germans some of the best trained in Africa at the time? I could be mistaken though my knowledge of the German East Africa Company is minimal at best.
They certainly were by WW1, but I suspect that they may not have attained that standard yet in the late 19th century. At this stage their reputation was built on fighting native warriors, but they had not yet faced European troops.
In the Queen's Own African Rifles list in HVF:
British privates have Pluck 5+ FV+2 SV+2 Bayonet Drill - Brigandine, Military Rifle, Bayonet
African privates (askaris) have Pluck 5+ FV+1 SV+1 Speed+1 Bayonet Drill - Lined Coat, Military Rifle, Bayonet
If you want your German askaris to be a bit better than the British equivalent I would give them FV+2:
German Askari: Pluck +5 FV+2 SV+1 Speed+1 Bayonet Drill - Lined Coat, Military Rifle, Bayonet = 21 Points