I used atronarch for non-mage characters. The huge magicka absorbtion makes you really good against mages and since you don't need magicka to begin with, the slower regen won't matter.

That's a really good idea
It's a shame that Steed is so almost-stupidly OP though that I never don't want to use it.
It worked better in older games when the Steed birthsign simply made you run faster. Now since they have everything go at the same speed, they changed it to making you be able to carry more and no longer suffer movement penality with heavy armor.
Sounds not too bad, until you realize it adds almost 100lbs worth of carryweight...then it becomes "must have" :\