Well, they do get +1 AS, increased movement, better LoS (works both ways, of course) and either a 6+ ward or +1 to Hit. Perhaps the idea was, if you would take wizard and wand wagon anyway, why not combine them? But the benefits clearly do not outweigh the disadvantages as a wizard mount.
And speaking of mounts, the War Altar should at least confer it's 4+ Ward save to anyone riding on it, thereby freeing up points to give the AL other magic items; for example:
Fr. Jorg Junkers(100), with the Ogre Hammer(40), heavy armour(4), the Enchanted shield(5), Van Horstmann's Speculum(40) and the Other Trickster's Shard(15). 204 pts
Or, if you don't think the more expensive +S items are worth their cost, something like this:
Fr. Jorg Junkers(100), with the Fencer's Blades(35), the Armour of Meteoric Iron(50) and the Other Trickster's Shard(15). 200 pts