I don't think Set is underpowered.... Honest..
It's just that most people can't use his bonus right! I rarely pick Egipt, and i never play Isis, but i do enjoy Set and Ra.
I think Set plays a little different from the other Egipcian Gods, however i don't play him much, so i may be mistaken.
Anyway, Ra and Isis usually try to FH, or at least semi FH, while Set can allow himself to stick to classical for a while, due to the animals and great slingers! Of course, Midgols are cheaper and all, but that just isn't as tempting as Ra's Camelry and CA, or Isis Uber Combo Eclipse-Ancestors...
Maybe i'm doing way wrong, but i liek to harass my enemy with a couple anubites backed up by some slingers can really be painful against Norse, with their non-ranged-low-pierce-armor Heros... And anubites really hold their ground against Rc.. Since Ulfsarks also have low Pierce armor, there is only 1 unit that can harm you, that is the Troll. Some trolls easily deal with your anubites because they act like Ranged heros.
Also, since your slingers only use wood/gold, it's relatively easy to mass Anubites. If not, train some spearman to deal with the RC.
It's just an idea... I may be waaaaaaay wrong... Just let some set expert say something..
"He had decided to live forever or die in the attempt."
J. Heller